NCERT Exemplar Problems Class 11 Chemistry Chapter 3 Classification of Elements and Periodicity in Properties

Multiple Choice Questions
Single Correct Answer Type

Q1. Consider the isoelectronic species, Na⁺, Mg²⁺, F and O^2-. The correct order of increasing length of their radii is

Sol: (b) Amongst isoelectronic ions, ionic radii decrease with increase in nuclear charge:
Mg²⁺(12) < Na⁺(11) < F (10) < 0^2- (8)

Q2. Which of the following is not an actinoid?
(a) Curium (Z = 96)
(b)Californium (Z = 98)
(c) Uranium (Z = 92)                               
(d)    Terbium (Z = 65)
Sol: (d) Actinoids are elements with Z= 90 – 103. Therefore, Terbium (Z = 65) is not an actinoid. Terbium (Z = 65) is a lanthanoid. Tb: [Xe]4f⁹5d⁰6s²

Q3. The order of screening effect of electrons of s, p, d and/orbitals of a given shell of an atom on its outer shell electrons is
(a) s>p> d>f
(b) f> d> p> s
(c) p < d < s <f
(d) f> p> s> d
Sol: (a) The screening effect of the orbitals follows the order of s >p > d>f as screening effect decreases from s-orbital to f-orbital in an atom on account of shape of the orbital.

Q4. The first ionization enthalpies of Na, Mg, A1 and Si are in the order
(a)    Na < Mg > A1 < Si                          
(b)     Na>Mg>Al>Si
(c)    Na < Mg < A1 < Si                          
(d)    Na > Mg > A1 < Si

Sol: (a) The electronic configurations of Na and Mg are:

Na (11): [Ne] 3s¹ and Mg (12): [Ne] 3s² In both the atoms, the electron is to be removed from 3s-orbital but nuclear charge in Na is less than Mg. Thus, ionisation energy of Na is less than Mg (Na < Mg).
The electronic configurations of Mg and Al are:
Mg: [Ne] 3s²; Al: [Ne] 3s² 3p^l
In Mg, the electron is to be removed from 3s-orbital while in Al, it is to be removed from 3p-orbital. Since it is easier to remove an electron from 3p-orbital in comparison to 3s-orbital, the ionization enthalpy of Mg is higher than Al (Mg > Al).
The electronic configurations of Al and Si are:
Al (13): [Ne] 3s² 3p¹ Si (14): [Ne] 3s² 3p²
In both the atoms, the electron is to be removed from 3p-orbital but nuclear charge in Si is more than Al. Thus, ionisation enthalpy of Al is less than Si

Q5. The electronic configuration of gadolinium (Atomic number 64) is


Sol: (c) The electronic configuration of La (Z = 57) is [Xe] 5d^l 6s². Therefore, further addition of electrons occurs in the lower energy 4f-orbital till it is exactly half-filled at Eu (Z = 63) Thus, the electronic configuration of Eu is [Xe] 4f⁷ 6s². Thereafter, addition of next electron does not occur in the more stable exactly half-filled 4f⁷ shell but occurs in the little higher energy 5d-orbital. Thus, the electronic configuration of Gd (Z = 64) is [Xe] 4f⁷ 5d^l 6s².

Q6. The statement that is not correct for periodic classification of elements is
(a) The properties of elements are periodic function of their atomic numbers.
(b) Non-metallic elements are less in number than metallic elements.
(c) For transition elements, the 3d-orbitals are filled with electrons after 3p-orbitals and before 4s-orbitals.
(d) The first ionization enthalpies of elements generally increase with increase in atomic number as we go along a period.
Sol: (c) For transition elements, the 3d-orbitals are filled with electrons after 3p and 4s-orbitals and before 4p-orbitals. The order of filling the orbitals is:
Is 2s 2p 3s 3p 4s 3d4p 5s 4d 5p 6s …

Q7. Among halogens, the correct order of amount of energy released in electron gain (electron gain enthalpy) is
(a) F > Cl > Br > I
(b) F < Cl < Br < I
(c) F < Cl > Br > I
(d) F < Cl < Br > I
Sol: (c) Chlorine has higher electron gain enthalpy than fluorine. This is due to small size of fluorine atom, i.e., the electron density is high which resists the addition of an electron (F < Cl).
In general, electron gain enthalpy decreases as atomic size increases. Thus, electron gain enthalpy follows the order:
Cl > Br > I

Q8. The period number in the long form of the periodic table is equal to
(a) magnetic quantum number of any element of the period.
(b) atomic number of any element of the period.
(c) maximum principal quantum number of any element of the period.
(d) maximum Azimuthal quantum number of any element of the period.
Sol: (c) Since each period starts with the filling of electrons in a new principal quantum number, therefore, the period number in the long form of the periodic table refers to the maximum principal quantum number of any element in the period.
Period number = maximum n of any element
(where, n = principal quantum number).

Q9. The elements in which electrons are progressively filled in 4f-orbital are called
(a) actinoids.
(b) transition elements.
(c) lanthanoids.
(d) halogens.
Sol: (c) In lanthanoids, the electrons are filled in 4f-orbitals.

Q10. Which of the following is the correct order of size of the given species?
(a) I>I>I⁺
(b) I⁺>I^–>I
(c) i>i⁺>i^–
(d) i^– >i>i⁺

Sol: Anion is bigger than the parent atom and cation is smaller than the parent atom.
Thus, I^– > I > I⁺

Q11.  The formation of the oxide ion, 0^2-(g), from oxygen atom requires first an exothermic and then an endothermic step as shown below:
O(g) + e^–→0^– (g), ∆H= -141 kJ mol^-1
0^–(g) + e^–→O² (g), ∆H = +780 kJ mol^-1
Thus process of formation of O^2- ion in gas phase is unfavourable even though O^2- is isoelectronic with neon. It is due to the fact that

(a) Oxygen is more electronegative.
(b) Addition of electron in oxygen results in larger size of the ion.
(c) Electron repulsion outweighs the stability gained by achieving noble gas configuration.
(d) 0^– ion has comparatively smaller size than oxygen atom.
Sol:(c) There is a lot of repulsion when similar charges approach each other as
O^–(g), and electron are both negatively charged. To add an electron under such situation, the force of repulsion is to be overcome by applying external energy.

Q12. Comprehension given below is followed by some multiple choice questions. Each question has one correct option.
In the modem periodic table, elements are arranged in order of increasing atomic numbers which is related to the electronic configuration. Depending upon the type of orbitals receiving the last electron, the elements in the periodic table have been divided into four blocks, viz, s,p, d and f The modem periodic table consists of 7 periods and 18 groups. Each period begins with the filling of a new energy shell. In accordance with the Aufbau principle, the seven periods (1 to 7) have 2, 8, 18, 18, 32 and 32 elements respectively. The seventh period is still incomplete. To avoid the periodic table being too long, the two series of f-block elements, called lanthanoids and actinoids, are placed at the bottom of the main body of the periodic table.
(i) The element with atomic number 57 belongs to
(a) s-block
(b) p-block
(c)  d-block
(d)  f-block

(ii) The last element of the p-block in 6^th period is represented by the outermost electronic configuration.

(a)    7s² 7p⁶
(b)     5f¹⁴ 6d¹⁰ 7s² 7p⁰
(c)     4f¹⁴ 5dⁱ⁰ 6s²6
(d)     4f¹⁴ 5dⁱ⁰     6s² 6p⁴

(iii) Which of the elements whose atomic numbers are given below, cannot be accommodated in the present set up of the long form of the periodic table?

(a) 107
(b) 118
(c) 126               .
(d) 102

(iv) The electronic configuration of the element which is just above the element with atomic number 43 in the same group is________ .

(a) 1s² 2s²2p⁶ 3s² 3p⁶ 3d⁵ 4s²
(b) 1s² 2s² 2p⁶ 3 s² 3p⁶ 3d⁵ 4s³ 4p⁶
(c) 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵ 4s²
(d) ls² 2s² 2p⁶ 3s² 3p⁶ 3d⁷4s²

(v) The element with atomic number 35, 53 and 85 are all_____ .

(a) noble gases
(b) halogens
(c) heavy metals
(d) light metals

Q13. Electronic configurations of four elements A, B, C and D are given below:
(A) 1s² 2s¹2p⁶             
(B)  1 s² 2s² 2p⁴
(C)     1s² 2s² 2p⁶ 3s¹                                  
(D)    Is² 2s² 2p⁵

Which of the following is the correct order of increasing tendency to gain electron?

(a) A < C < B < D
(b)     A < B < C < D
(c)    D < B < C < A                                 
(d)     D < A< B < C

Sol. (a) A – Is² 2s² 2p⁶ – Noble gas configuration

B -1s² 2s² 2p⁴ – 2 electrons short of stable configuration

C – 1s² 2s² 2p⁶ 3.?¹ – Requires one electron to complete 5-orbital

D -1s² 2s² 2p⁵ – Requires one electron to attain noble gas configuration

• Noble gases have no tendency to gain electrons since all their orbitals are completely filled. Thus, element A has the least electron gain enthalpy.
• Since element D has one electron less and element B has two electrons less than the corresponding noble gas configuration, hence, element D has the highest electron gain enthalpy followed by element B.
• Since, element C has one electron in the 5-orbital and hence needs one more electron to complete it, therefore, electron gain enthalpy of C is less than that of element B. Combining all the facts given above, the electron gain enthalpies of the four elements increase in the order A < C < B < D.

More than One Correct Answer Type
Q14. Which of the following elements can show covalency greater than 4?
(a) Be (b) P (c) S (d) B
Sol: (b, c) P and S have d-orbitals in their valence shell and therefore, can accommodate more than 8. electrons in their respective valence shells. Hence they show covalency more than 4.

Q15. Those elements impart colour to the flame on heating in it, the atoms of which require low energy for the ionization (i.e., absorb energy in the visible region of spectrum). The elements of which of the following groups will impart colour to the flame?
(a) 2 (b) 13 (c) 1 (d) 17
Sol: (a, c) The elements of group 1 (alkali metals) and group 2 (alkaline earth metals) have low ionization enthalpies. Therefore, they impart colour to flame.

Q16. Which of the following sequences contain atomic numbers of only representative elements?
(a) 3, 33, 53, 87
(b) 2, 10, 22, 36
(c) 7, 17,25,37,48
(d) 9,35,51,88
Sol: (a, d) Elements of 5 and p-block elements are called representative elements. Elements of f-block (Z=21 – 30; 39 – 48; 57 and 72 – 80; 89 and 104 – 112) are called transition elements while those of f-block (with Z = 58-71 and Z = 90 – 103) are called inner transition elements.
(a) 3 – Group 1, 33 – group 15, 53 – group 17 and 87 – group 1.
(d) 9 – Group 17, 35 – Group 17, 51 – Group 15, 88 – Group 2.

Q17. Which of the following elements will gain one electron more readily in comparison to other elements of their group?
(a) S (g) (b) Na (g) (c) O (g) (d) Cl(g)
Sol:(a, d) Chlorine has highest tendency to gain an electron and its electron gain enthalpy (-ve) is high. O and S belong to group 16 but S has larger tendency to accept electron.

Q18. Which of the following statements are correct?
(a) Helium has the highest first ionization enthalpy in the periodic table.
(b) Chlorine has less negative electron gain enthalpy than fluorine.
(c) Mercury and bromine are liquids at room temperature.
(d) In any period, atomic radius of alkali metal is the highest.
Sol: (a, c, d) Chlorine has more negative electron gain enthalpy than fluorine due to bigger size and lesser electronic repulsion.

Q19. Which of the following sets contain only isoelectronic ions?
(a) Zn²⁺, Ca²⁺, Ga³⁺, Al³⁺                       
(b) K⁺, Ca²⁺, Sc³⁺, Cl^–
(c) P^3-, S^2- Cl^–,K⁺                          
(d) Ti⁴⁺, Ar, Cl³⁺, V⁵⁺
Sol: (b, c)
(a) Zn²⁺ (30 – 2 = 28), Ca²⁺ (20 – 2 = 18), Ga³⁺ (31-3= 28), Al³⁺ (13 – 3 = 10) are not isoelectronic.
(b) K⁺ (19 – 1 = 18), Ca²⁺ (20 – 2 = 18), Sc³⁺ (21 – 3 = 18), Cl^– (17 + 1 = 18) are isoelectronic.
(c) P^3- (15 + 3 = 18), S^2- (16 + 2 = 18), Cl^– (17 + 1 = 18), K⁺ (19 – 1 = 18) are isoelectronic.
(d) Ti⁴⁺ (22 – 4 = 18), Ar (18), Cr³⁺ (24 – 3 = 21), V⁵⁺ (23 – 5 = 18) are not isoelectronic.

Q20. In which of the following options order of arrangement does not agree with the variation of property indicated against it?
(a) Al³⁺ < Mg²⁺ < Na⁺ < F^– (increasing ionic size)
(b) B < C < N < O (increasing first ionization enthalpy)
(c) I < Br < Cl < F (increasing electron gain enthalpy)
(d) Li < Na < K < Rb (increasing metallic radius)
Sol: (b, c) For increasing first ionization enthalpy, the order should be:
B < C < O < N
For increasing electron gain enthalpy, the order should be:
I < Br < F < Cl

Q21. Which of the following have no unit?
(a) Electronegativity (b) Electron gain enthalpy
(c) Ionisation enthalpy (d) Metallic character
Sol: (a, d) Electron gain enthalpy and ionization enthalpy have units of enthalpy.

Q22. Ionic radii vary in
(a) inverse proportion to the effective nuclear charge.
(b) inverse proportion to the square of effective nuclear charge.
(c) direct proportion to the screening effect.
(d) direct proportion to the square of screening effect.
Sol: (a, c) Ionic radii decreases as the effective nuclear charge increases.

Q23. An element belongs to 3^rd period and group-13 of the periodic table. Which of the following properties will be shown by the element?
(a) Good conductor of electricity
(b) Liquid, metallic
(c) Solid, metallic  
(d) Solid, non metallic
Sol:(a, c) The element belonging to 3^rd period and 13^th group is aluminium which is a metal. Hence, it is solid, metallic and good conductor of electricity.

Short Answer Type Questions
Q24. Explain why the electron gain enthalpy of fluorine is less negative than that of chlorine.
Sol: In fluorine, the new electron to be added goes to 2p-subshell while in chlorine, the added electron goes to 3p-subshell. Since the 2p-subshell is relatively small as compared to 3p-subshell, the added electron in small 2p-subshell experiences strong interelectronic repulsions in comparison to that in 3p-subshell in Cl. As a result, the incoming electron does not feel much attraction from the nucleus and therefore, the electron gain enthalpy of F is less negative than that of Cl.

Q25. All transition elements are d-block elements, but all d-block elements are not transition elements. Explain.
Sol: All the elements in between s- and p-block, i.e., between group 2 and 13 are called transition elements. Elements in which the last electron enters the d-orbitals of their respective penultimate shells are called d-block elements. According to this definition, Zn, Cd and Hg cannot be regarded as d-block elements because last electron in these elements enters the s-orbital of their outermost shells rather than d-orbital of their penultimate shells. Therefore, these elements should not be regarded as d-block elements. However, the properties of these elements resemble with cf-block elements. Therefore, to make the study of periodic classification of elements more rational, these are studied along with d-block elements. Thus, on the basis of properties, all the transition elements are d-block elements but on the basis of electronic configuration, all d-block elements are not transition elements.

Q26. Identify the group and valency of the element having atomic number 119. Also predict the outermost electronic configuration and write the general formula of its oxide.
Sol: The present set up of the Long Form of the Periodic Table can accommodate at the maximum 118 elements. After this, according to Aufbau principle, 8.y-orbital should be filled. Therefore, the outer electronic configuration of element having atomic number 119 will be 8s¹. Since it has one electron in the outermost s-orbital, its valency will be 1 and it should belong to group 1 along with alkali metals. The general formula of its oxide will be M₂0, where M represents the element.

Q27. Ionisation enthalpies of elements of second period are given below:
Ionisation enthalpy/kJ mol-1: 520, 899, 801, 1086, 1402, 1314, 1681, 2080. Match the correct enthalpy with the elements and complete the graph given in figure. Also write symbols of elements with their atomic number.

Sol: To match the correct enthalpy with the elements and to complete the graph, the following points are taken into consideration. As we move from left to right across a period, the ionization enthalpy keeps on increasing due to increased nuclear charge and simultaneous decrease in atomic radius. However, there are some exceptions given below-                                                                                                                    –

• In spite of increased nuclear charge, the first ionisation enthalpy of B is lower than that of Be. This is due to the presence of fully filled 2s-orbital of Be [1s²2s²] which is a stable electronic arrangement. Thus, higher energy is required to knock out the electron from fully filled 2.v-orbital. While B [1s² 2s² 2p¹] contains valence electrons in 2s and 2p-orbitals. It can easily lose its one e^– from 2p-orbital in order to achieve noble gas configuration. Thus, first ionisation enthalpy of B is lower than that of Be.
  Since the electrons in 2s-orbital are more tightly held by the nucleus than those present in 2p-orbital, therefore, ionisation enthalpy of B is lower than that of Be.

• The first ionisation enthalpy of N is higher than that of O though the nuclear charge of O is higher than that of N. This is due to the reason that in case of N, the electron is to be removed from a more stable, exactly half-filled electronic configuration (1s² 2s² 2¹_x2p^l_y 2p¹_z) which is not present in O (1s² 2s² 2p²_x 2p¹_y 2p¹_z).
  Therefore, the first ionisation enthalpy of N is higher than that of O. The symbols of elements along with their atomic numbers are given in the following graph

Q28. Among the elements B, Al, C and Si,
(a) which element has the highest first ionization enthalpy
(b) which element has the most metallic character?
Justify your answer in each case.
Sol: Arranging the elements into different groups and periods:

• Ionization enthalpy increases along a period and decreases down a group. Therefore, C has the highest first ionization enthalpy.
• Metallic character decreases along a period and increases down a group. Therefore, Al has the most metallic character.

Q29. Write four characteristic properties of p-block elements.
Sol: The four important characteristic properties of p-block elements are the following:
(a) p-Block elements include both metals and non-metals but the number of non-metals is much higher than that of metals. Further, the metallic character increases from top to bottom within a group and non-metallic character increases from left to right along a period in this block.
(b) Their ionization enthalpies are relatively higher as compared to s-block elements.
(c) They mostly form covalent compounds.
(d) Some of them show more than one (variable) oxidation states in their compounds. Their oxidizing character increases from left to right in a period and reducing character increases from top to bottom in a group.

Q30. Choose the correct order of atomic radii of fluorine and neon (in pm) out of the options given below and justify your answer.
(i) 72,160 (b) 160,160 (c) 72,72 (d) 160,72
Sol:(i) Atomic radius decreases as we move from left to right in a period in the periodic table. Fluorine has the smallest atomic radius. As we move to neon
in the same period, the atomic radius increases as it has van der Waals radius and van der Waals radii are bigger than covalent radii.

Q31. Illustrate by taking examples of transition elements and non-transition elements that oxidation states of elements are largely based on electronic configuration.
Sol: The oxidation state of an element is based on its electronic configuration. The various oxidation states of a transition metal are due to the involvement of (n-1)d and outer ns electrons in bonding.
For example, Ti (22, electronic configuration [Ar]3d²4s²) can show three oxidation states (+2, +3 and +4) in various compounds like Ti0₂ (+4), Ti₂0₃ (+3) and TiO (+2).
The non-transition elements, mainly thep-block elements can show a number of oxidation states from +n to (n – 8) where, n is the number of electrons present in the outermost shell. For example, phosphorus can show -3, +3 and +5 oxidation states.
Lower oxidation states are ionic as the atom accepts the electron or electrons to achieve stable configuration while higher oxidation states are achieved by unpairing the paired electrons and shifting the electrons to vacant d-orbital.

Q32. Nitrogen has positive electron gain enthalpy whereas oxygen has negative. However, oxygen has lower ionization enthalpy than nitrogen explain.
Sol: The outermost electronic configuration of nitrogen is 2s²2p¹_x2p¹_y2p¹_z. It is stable because it has exactly half filled 2p-subshell. Therefore, it has no tendency to accept extra electron and energy has to be supplied to add additional electron. Thus, electron gain enthalpy of nitrogen is slightly positive. On the other hand, the outermost electronic configuration of O is 2s²2p²_x2p¹_y2p¹_z. It has higher positive charge (+8) than nitrogen (+7) and lower atomic size than N. Therefore, it has a tendency to accept an extra electron. Thus, electron gain enthalpy of O is negative. However, oxygen has four electrons in the 2p subshell and can lose one electron to acquire stable half filled configuration and therefore, it has low ionization enthalpy. Because of stable configuration of N, it cannot readily lose electron and therefore, its ionization enthalpy is higher than that of O.

Q33. First member of each group of representative elements (i.e., s and p-block elements) shows anomalous behaviour. Illustrate with two examples.
Sol:First member of each group of s- and p-block elements shows anomalous behaviour due to the following reasons:
(i) Small size
(ii) High ionization enthalpy
(iii) High electronegativity
(iv) Absence of d-orbitals
Examples: Li in the first group shows different properties from the rest of elements like covalent nature of its compounds, formation of nitrides.

Similarly, beryllium, the first element of second group differs from its own group in the following ways:

• Beryllium carbide reacts With water to produce methane gas while carbides of other elements give acetylene.
• Beryllium shows a coordination number of four while other elements show a coordination number of six.

Q34. p-Block elements form acidic, basic and amphoteric oxides. Explain each property by giving two examples and also write the reactions of these oxides with water.
Sol:In p-block, when we move from left to right in a period, the acidic character of the oxides increases due to increase in electronegativity. For example,

• In 2^nd period B₂0₃ < C0₂ < N₂0₃ (acidic nature increases).
• In 3^rd period A1₂0₃ < Si0₂ < P₄O₁₀ < S0₃ < C1₂0₇ (acidic character increases).

On moving down the group, acidic character decreases and basic character increases, e.g.,

Among the oxides of same element, higher the oxidation state of the element, stronger is the acid. For example, S0₃ is a stronger acid than S0₂.
B₂0₃ is weakly acidic and on dissolution in water, it forms orthoboric acid. Orthoboric acid does not act as a protonic acid (it does not ionise) but acts as a weak Lewis acid.

Q35. How would you explain the fact that first ionization enthalpy of sodium is lower than that of magnesium but its second ionization enthalpy is higher than that of magnesium?
Sol: Electronic configuration of Na is 1s²2s²2p⁶3s¹. After losing one electron from its outermost shell, sodium easily attains stable electronic configuration (1s²2s²2p⁶ ), while magnesium does not lose its electron easily due to presence of two electrons in s-orbital (ls²2s²2p⁶3s²). Hence first ionisation energy of sodium is less than magnesium.
When one electron is removed from Na and Mg, their configurations become ls²2s²2p⁶ and 1s²2s²2p⁶3s¹ respectively. Now it is easier to remove one electron from 3s of Mg⁺ than 2p⁶ of Na⁺. Hence, second ionisation energy of Mg is less than Na.

Q36. What do you understand by exothermic reaction and endothermic reaction? Give one example of each type.
Sol:Exothermic reaction: The reaction which is accompanied with evolution of heat is known as exothermic reaction.
CaO + C0₂ → CaC0₃, ΔH= -178.3 kJ mol^-1
Endothermic reaction: The reaction which is accompanied with absorption of energy is known as endothermic reaction, e.g.,
2NH₃ → N₂ + 3H₂; ΔH = +91.8 kJ mol^-1

Q37. Arrange the elements N, P, O and S in the order of
(i) increasing first ionisation enthalpy.
(ii) increasing non-metallic character.
Give reason for the arrangement assigned.
Sol: (i) S < P < O < N
Ionisation enthalpy increases from left to right in a period and decreases down the group. N has higher ionisation enthalpy than O due to extra stability of half-filled orbitals. Similarly, P has higher ionisation enthalpy than S due to half-filled orbitals.
(ii) P < S < N < O
Non-metallic character decreases down the group and increases from left to right in a period.

Q38. Explain the deviation in ionization enthalpy of some elements from the general trend by using the given figure.

Sol: Ionisation enthalpy increases in a period with increase in atomic number. The graph shows few exceptions and not the linear relationship. Ionisation enthalpy of Be is greater than that of B due to filled s-orbital in Be (Be – l.s² 1s², B – 1s² 2s² 2p^l).
Ionisation enthalpy of N is greater than that of O due to half-filled/?-orbitals in nitrogen.
(N – Is² 2s ²2p³ O – ls ² 2s² 2p⁴).

Q39. Explain the following:
(a) Electronegativity of elements increases on moving from left to right in the periodic table.
(b) Ionisation enthalpy decreases in a group from top to bottom.
Sol: (a) The electronegativity generally increases on moving across a period from left to right (e.g., from Li to F in the second period). This is due to decrease in atomic size and increase in effective nuclear charge. As a result of increase in effective nuclear charge, the attraction for the outer electron and the nucleus increases in a period and therefore, electronegativity also increases.
(b) On moving down a group there is a gradual decrease in ionisation enthalpy. The decrease in ionisation enthalpy down a group can be explained in terms of net effect of the following factors:
(i) In going from top to bottom in a group, the nuclear charge increases.
(ii) There is a gradual increase in atomic size due to an additional main energy shell (n).
(iii) There is increase in shielding effect on the outermost electron due to increase in the number of inner electrons.
The effect of increase in atomic size and the shielding effect is much more than the effect of increase in nuclear charge. As a result, the electron becomes less and less firmly held to the nucleus as we move down the group. Hence, there is a gradual decrease in the ionization enthalpies in a group.

Q40. How does the metallic and non metallic character vary on moving from left to right in a period?
Sol: As we move from left to right in a period, the number of valence electrons increases by one at each succeeding element but number of shells remains same. Due to this, effective nuclear charge increases. More is the effective nuclear charge, more is the attraction between the nucleus and electron.
Hence, the tendency of the element to lose electrons decreases. This results in decrease in metallic character. Furthermore, the tendency of an element to gain electrons increases with increase in effective nuclear charge, so non- metallic character increases on moving from left to right in a period.

Q41. The radius of Na⁺ cation is less than that of Na atom. Give reason.
Sol: The radius of Na⁺ is less than Na atom because Na⁺ is formed by losing one energy shell.
Na – 1s² 2s² 2p⁶ 3s¹
Na⁺– 1s²2s² 2p⁶

Q42. Among alkali metals which element do you expect to be least electronegative and why?  
Sol: Cs is the most electropositive or least electronegative element among the alkali metals since electronegative character decreases in a group.

Matching Column Type Questions
Q43. Match the correct atomic radius with the element.

Sol: All the given elements are of same period and along period, atomic radii decrease because effective nuclear charge increases. Thus, the order of atomic radii is
O < N < C < B < Be or, Be = 111 pm, O = 66 pm, C = 77 pm, B = 88 pm, N = 74 pm.

Q44. Match the correct ionization enthalpies and electron gain enthalpies of the following elements.

Q45. Electronic configurations of some elements are given in column I and their electron gain enthalpies are given in column II. Match the electronic configuration with electron gain enthalpy.

Assertion and Reason Type Questions
In the following questions a statement of Assertion (A) followed by a statement of Reason (R) is given. Choose the correct option out of the choices given below each question.
Q46. Assertion (A): Generally, ionization enthalpy increases from left to right in a period.
Reason (R): When successive electrons are added to the orbitals in the same principal quantum level, the shielding effect of inner core of electrons does not increase very much to compensate for the increased attraction of the electron to the nucleus.
(a) Assertion is correct statement and reason is wrong statement.
(b) Assertion and reason both are correct statements and reason is correct explanation of assertion.
(c) Assertion and reason both are wrong statements.
(d) Assertion is wrong statement and reason is correct statement.
Sol: (b) Ionisation enthalpy increases from left to right across the period due to decrease in atomic size.
The electrons present within the subshell has almost same effective nuclear charge.

Q47. Assertion (A): Boron has a smaller first ionization enthalpy than beryllium. Reason (R): The penetration of a 2s electron to the nucleus is more than the 2p electron, hence, 2p electron is more shielded by the inner core of electrons that the 2s electrons.
(a) Assertion and reason both are correct statements but reason is not correct explanation of assertion.
(b) Assertion is correct statement but reason is wrong statement.
(c) Assertion and reason both are correct statements and reason is correct explanation of assertion.
(d) Assertion and reason both are wrong statement.

Sol: (c) Boron (1s²2s²2p¹) has less first ionisation enthalpy than beryllium (1s²2s²) because beryllium has fully filled .s-subshell.
2s-electrons are nearer to the nucleus as compared to 2s-electrons.

Q48. Assertion (A): Electron gain enthalpy becomes less negative as we go down a group.
Reason (R): Size of the atom increases on going down the group and the added electron would be farther from the nucleus.
(a) Assertion and reason both are correct statements but reason is not correct explanation of assertion.
(b) Assertion and reason both are correct statements and reason is correct explanation of assertion.
(c) Assertion and reason both are wrong statement.
(d) Assertion is wrong statement but reason is correct statement.
Sol:(b) On moving down the group, the electron gain enthalpy becomes less negative because on moving down the group the atomic size increases and the added electron lies away from the nucleus.

Long Answer Type Questions
Q49. Discuss the factors affecting electron gain enthalpy and the trend in its variation in the periodic table.
Sol: Factors affecting electron gain enthalpy:
(i) Nuclear charge: The electron gain enthalpy become more negative as the nuclear charge increases. This is due to greater attraction for the incoming electron if nuclear charge is high.
(ii) Size of the atom: With the increase in size of the atom, the distance between the nucleus and the incoming electron increases and this results in lesser attraction. Consequently, the electron gain enthalpy become less negative with increase in size of the atom of the element.
(iii) Electronic configuration: The elements having stable electronic configurations of half filled and completely filled valence subshells show very small tendency to accept additional electron and thus electron gain enthalpies are less negative.

Variation of electron gain enthalpies in periodic table:
Electron gain enthalpy, in general, becomes more negative from left to right in a period and becomes less negative as we go from top to bottom in a group.
(a) Variation down a group: On moving down a group, the size and nuclear charge increases. But the effect of increase in atomic size is much more pronounced than that of nuclear charge and thus the additional electron feels less attraction by the large atom. Consequently, electron gain enthalpy becomes less negative. This is clear from decrease of electron gain enthalpy in going from chlorine to bromine and to iodine.
(b) Variation along a period: On moving across a period, the size of the atom decreases and nuclear charge increases. Both these factors result in greater attraction for the incoming electron, therefore, electron gain enthalpy, in general, becomes more negative in a period from left to right. However, certain irregularities are observed in the general trend. These are mainly due to the stable electronic configurations of certain atoms.
Important Trends in Electron Gain Enthalpies:
There are some important features of electron gain enthalpies of elements. These are:
(i) Halogens have the highest negative electron gain enthalpies.
(ii) Electron gain enthalpy values of noble gases are positive while those of Be, Mg, N and P are almost zero.
(iii) Electron gain enthalpy of fluorine is unexpectedly less negative than that of chlorine.

Q50. Define ionization enthalpy. Discuss the factors affecting ionisation enthalpy of the elements and its trends in the periodic table.
Sol: Ionisation enthalpy: It is defined as the minimum amount of energy required to remove the most loosely bound electron from an isolated gaseous atom.

M(g) →M⁺(g) + e^–I₁  = First ionisation enthalpy

Similarly, second and third electrons are also removed by providing successive ionisation enthalpies.

Factors on which Ionisation Enthalpy Depends:
(i) Size of the atom: The larger the atomic size, smaller is the value of ionisation enthalpy. In a larger atom, the outer electrons are far away from the nucleus and thus force of attraction with which they are attracted by the nucleus is less and hence can be easily removed.

Ionisation enthalpy ∝ 1/ Atomic size

(ii) Screening effect: Higher the screening effect, the lesser is the value of ionisation enthalpy as the screening effect reduces the force of attraction towards nucleus and hence the outer electrons can be easily removed.

Ionisation enthalpy ∝  1/ Screening effect

(iii) Nuclear charge: As the nuclear charge increases among atoms having same number of energy shells, the ionisation enthalpy increases because the force of attraction towards nucleus increases.

Ionisation enthalpy ∝ Nuclear charge

(iv) Half filled and fully filled orbitals: The atoms having half filled and fully filled orbitals are comparatively more stable, hence more energy is required to remove the electron from such atoms. The ionization enthalpy is rather higher than the expected value in case of such an atom.

Ionisation enthalpy ∝ Stable electronic configuration

(v) Shape of orbital: The s-orbital is more close to nucleus than the p-orbital of the same orbit. Thus, it is easier to remove electron from a p-orbital in comparison to s-orbital. In general, the ionisation enthalpy follows the following order

(s>p> d>f) orbitals of the same orbit.

Variation of ionisation enthalpy in the periodic table
ln general, the ionisation energy decreases down the group due to increase in atomic size. On the other hand, the ionisation energy increases across the period from left to right, again due to decrease in atomic size from left to right.

Q51. Justify the given statement with suitable examples “the properties of the elements are a periodic function of their atomic numbers”.
Sol. The similarities in the properties arise due to the same distribution of electrons in the outermost orbitals or electronic configuration which depends upon the atomic number. The elements present in a group or period exhibit similar chemical properties which depend upon the atomic number.

Q52. Write down the outermost electronic configuration of alkali metals. How will you justify their placement in group 1 of the periodic table?

Q53. Write the drawbacks in Mendeleev’s periodic table that led to its modification.
Sol: Drawbacks of Mendeleev’s periodic table:
1. Position of hydrogen: Hydrogen is placed in group I. However, it resembles the elements of group I (alkali metals) as well as the elements of group VILA, (halogens). Therefore, the position of hydrogen in the periodic table is not correctly defined.
2. Anomalous pairs: In certain pairs of elements, the increasing order of atomic masses was not obeyed. In these cases, Mendeleev placed elements according to similarities in their properties and not in increasing order of their atomic masses. For example, argon (Ar, atomic mass 39.9) is placed before potassium (K, atomic mass 39.1). Similarly, cobalt (Co, atomic mass 58.9) is placed before nickel (Ni, atomic mass 58.6) and tellurium (Te, atomic mass 127.6) is placed before iodine (I, atomic mass 126.9). These positions were not justified.
3. Position of isotopes: Isotopes are the atoms of the same element having different atomic masses but same atomic number. Therefore, according to Mendeleev’s classification, these should be placed at different places depending upon their atomic masses. For example, isotopes of hydrogen with atomic masses 1,2 and 3 should be placed at three places. However, isotopes have not been given separate places in the periodic table.
4. Some similar elements are separated and dissimilar elements are grouped together: In the Mendeleev’s periodic table, some similar elements were placed in different groups while some dissimilar elements
had been grouped together. For example, copper and mercury resembled
in their properties but they had been placed in different groups. At the same time, elements of group IA such as Li, Na and K were grouped with copper (Cu), silver (Ag) and gold (Au), though their properties are quite different.
5. Cause of periodicity: Mendeleev did not explain the cause of periodicity among the elements.
6. Position of lanthanoids (or lanthanides) and actinoids (or actinides):
The fourteen elements following lanthanum (known as lanthanoids, from atomic number 58-71) and the fourteen elements following actinium (known as actinoids, from atomic number 90 – 103) have not been given separate places in Mendeleev’s table.
In order to cover more elements, Mendeleev modified his periodic table.

Q54. In what manner is the long form of periodic table better than Mendeleev’s
periodic table? Explain with examples.
Sol: Superiority of the Long form of the Table over Mendeleev’s Table:
(i) This table is based on a more fundamental property, i.e., atomic number.
(ii) It correlates the position of the elements with their electronic configurations more clearly.
(iii) The completion of each period is more logical. In a period as the atomic number increases, the energy shells are gradually filled up until an inert gas configuration is reached. It eliminates the even and odd series of IV, V, VI and VII periods of Mendeleev’s periodic table.
(iv) The position of VIIIth group  is appropriate in this table. All the transition elements have been brought in the middle as the properties of transition elements are intermediate between s- and p-block elements.
(v) Due to separation of two subgroups, dissimilar elements do not fall together. One vertical column accommodates elements with same electronic configuration thereby showing same properties.
(vi) In this table, a complete separation between metals and non-metals has been achieved. The non-metals are present in the upper right comer of the periodic table.
(vii) There is a gradual change in properties of the elements with increase in their atomic numbers, i.e., periodicity of properties can be easily visualized. The same properties o recurrence in properties occur after the intervals of 2, 8, 8, 18, 18 and 32 elements which indicates the capacity of various periods of the table.
(viii) This arrangement of elements is easy to remember and reproduce.

Q55. Discuss and compare the trend in ionization enthalpy of the elements of group 1 with those of group 17 elements.
Sol: The ionization enthalpies decrease regularly as we move down a group from one element to the other. This is evident from the values of the first ionisation enthalpies of the elements of group 1 (alkali metals) and group 17 elements as given in table and figure.

Given trend can be easily explaihed on the basis of increasing atomic size and screening effect as follows
(i) On moving down the group, the atomic size increases gradually due to the addition of one new principal energy shell at each succeeding element. Hence, the distance of the valence electrons from the nucleus increases.
Consequently, the force of attraction by the nucleus for the valence electrons decreases and hence the ionisation enthalpy should decrease.
(ii) With the addition of new shells, the shielding or the screening effect increases. As a result, the force of attraction of the nucleus for the valence electrons further decreases and hence the ionisation enthalpy should decrease.
(iii) Nuclear charge increases with increase in atomic number. As a result, the force of attraction by the nucleus for the valence electrons should increase and accordingly the ionisation enthalpy should increase.
The combined effect of the increase in the atomic size and the screening effect more than compensates the effect of the increased nuclear charges. Consequently, the valence electrons become less and less firmly held by the nuclear and hence the ionisation enthalpies gradually decrease as move down the group.

NCERT Exemplar Problems Class 11 Chemistry

The post NCERT Exemplar Problems Class 11 Chemistry Chapter 3 Classification of Elements and Periodicity in Properties appeared first on Learn CBSE.

NCERT Exemplar Problems Class 11 Chemistry Chapter 4 Chemical Bonding and Molecular Structure

Multiple Choice Questions
Single Correct Answer Type

Q1. Isostructural species are those which have the same shape and hybridization. Among the given species identify the isostructural pairs.
(a) [NF₃ and BF₃]
(b) [BF^–₄andNH⁺₄]
(c) [BC1₃ and BrCl₃]                             
(d) [NH₃ and N0^–₃ ]
Sol: (b) NF₃ is pyramidal whereas BF₃ is planar triangular.
BF^–₄ and NH⁺₄ ions both are tetrahedral.
BC1₃ is triangular planar whereas BrCl₃ is pyramidal.
NH₃ is pyramidal whereas N0₃ is triangular planar.

Q2. Polarity in a molecule and hence the dipole moment depends primarily on electronegativity of the constituent atoms and shape of a molecule. Which of the following has the highest dipole moment?
(a) C0₂
(b) HI                      
(c) H₂0                     
(d) S0₂
Sol: (c) H₂0 will have highest dipole moment due to maximum difference in electronegativity of H and O atoms.

Q3. The types of hybrid orbitals of nitrogen in N0₂, N0₃ and NH₄ respectively are expected to be
(a) sp, sp³ and sp²                                  
(b) sp, sp² and sp³
(c) sp², sp and sp³                                   
(d) sp², sp³ and sp
Sol: (b) The number of orbitals involved in hybridization can be determined by the application of formula:

where H = number of orbitals involved in hybridization
V= valence electrons of central atom
M= number of monovalent atoms linked with central atom
C = charge on the cation
A = charge on the anion

Q4. Hydrogen bonds are formed in many compounds e.g., H₂0, HF, NH₃. The boiling point of such compounds depends to a large extent on the strength of hydrogen bond and the number of hydrogen bonds: The correct decreasing order of the boiling points of above compounds is
(a) HF>H₂0>NH₃                        
(b) H₂0>HF>NH₃
(c) NH₃>HF>H₂0                       
(d) NH₃>H₂0>HF
Sol: (b) Strength of H-bonding depends on the electronegativity of the atom which follows the order: F > O > N .
Strength of H-bond is in the order:
H……. F > H…….. O > H…….. N
But each H₂0 molecule is linked to 4 other H₂0 molecules through H-bonds whereas each HF molecule is linked only to two other HF molecules.
Hence, correct decreasing order of the boiling points is H_zO > HF > NH₃.

Q5. In PO₄^3- ion the formal charge on the oxygen atom of P – O bond is
(a) +1                      (b) -1                        (c) -0.75                    (d) +0.75
Sol: (b) Formal charge of the atom in the molecule or ion = (Number of valence electrons in free atom) – (Number of lone pair electrons + 1/2 Number of bonding electrons)

Q6. In N0^–₃ ion, the number of bond pairs and lone pairs of electrons on nitrogen atom are
(a) 2, 2                    (b) 3, 1                      (c) 1,3                      (d) 4, 0
Sol: (d) In N-atom, number of valence electrons = 5
Due to the presence of one negative charge, number of valence electrons = 5 + 1 = 6. One O-atom forms two bonds (= bond) and two O-atom are shared with two electrons of N-atom.
Thus, 3 O-atoms are shared with 8 electrons of N-atom.
Number of bond pairs (or shared pairs) = 4
Number of lone pairs = 0

Q7. Which of the following species has tetrahedral geometry?

Q9. Which molecule/ion out of the following does not contain unpaired electrons?
(a) N⁺₂
(b) 0₂                        
(c) O₂^2-                    
(d) B₂

Q10. In which of the following molecule/ion all the bonds are not equal?
(a) XeF₄                 
(b) BF^–₄                    
(c) C₂H₄                  
(d) SiF₄
Sol: (c) C₂H₄ has one double bond and four single bonds. Bond length of double bond (C = C) is smaller than single bond (C – H).

Q11. In which of the following substances will hydrogen bond be strongest?
(a) HCl
(b) H₂0                     
(c) HI                      
(d) H₂S
Sol: (b) HC1, HI and H₂S do not from H-bonds. Only H₂0 forms hydrogen bonds. One H₂0 molecule forms four H-bonding.

Q12. If the electronic configuration of an element is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d² 4s² , the four electrons involved in chemical bond formation will be .
(a) 3p⁶
(b 3p⁶, 4s²          
(c)  3p⁶, 3d²         
(d) 3d¹,4s²

Sol:(d) In transition elements (n -1 )d and ns orbitals take part in bond formation.

Q13. Which of the following angle corresponds to sp² hybridisation?
(a) 90° (b)     120°                (c)     180°               (d) 109°
Sol: (b) sp² hybridisation gives three sp² hybrid orbitals which are planar triangular forming an angle of 120° with each other.

The electronic configurations of three elements A, B and C are given below.
Answer the questions from 14 to 17 on the basis of these configurations.
A ls²2s²2p⁶
B ls²2s²2p⁶3s²3p³
C ls²2s²2p⁶3s²3p^s

Q14. Stable form of A may be represented by the formula
(a) A
(b) A₂                    
(c) A₃                   
(d)  A₄
Sol: (a) The given electronic configuration shows that A represents noble gas because the octet is complete. A is neon which has 10 atomic number.

Q15. Stable form of C may be represented by the formula
(a) C
(b) C₂                     
(c) C₃                   
(d)  C₄
Sol: (b) The electronic configuration of C represent chlorine. Its stable form is dichlorine (Cl₂), i.e., C₂.

Q16. The molecular formula of the compound formed from B and C will be
(a) BC
(b) B₂C                 
(c)  BC₂                
(d)  BC₃
Sol: (d) B represent P and C represents Cl. The stable compound is PC1₃ i.e., BC₃.

Q17. The bond between B and C will be
(a) ionic
(b) covalent         
(c) hydrogen
(d) coordinate
Sol: (b) Both B and C are non-metals and therefore, bond formed between them will be covalent.

Q18. Which of the following order of energies of molecular orbitals of N₂ is correct?

Q19. Which of the following statements is not correct from the view point of molecular orbital theory?
(a) Be₂ is not a stable molecule.
(b) He₂ is not stable but He⁺₂ is expected to exist.
(c) Bond strength of N₂ is maximum amongst the homonuclear diatomic molecules belonging to the second period.

Thus, dinitrogen (N₂) molecule contains triple bond and no other molecule of second period have more than double bond. Hence, bond strength of N₂ is maximum amongst the homonuclear diatomic molecules belonging to the second period.
(d) It is incorrect. The correct order of energies of molecular orbitals in N₂ molecule is

Q20. Which of the following options represents the correct bond order?
(a) o₂>o₂>o⁺₂
(b) o^–₂<o₂<o₂
(c) o₂>o₂<o₂
(d) o^–₂<o₂>o⁺₂

Q21. The electronic configuration of the outermost shell of the most electronegative element is
(a) 2s²2p⁵
(b) 3s²3p⁵                               
(c) 4s²4p⁵                
(d) 5s²5p^s
Sol: (a) The electronic configuration represents
2s²2p⁵= fluorine = most electronegative element
3s²3p⁵ = chlorine
4s²4p⁵ = bromine
5s²5p⁵ = iodine

Q22. Amongst the following elements, whose electronic configurations are given below, the one having the highest ionization enthalpy is
(a) [Ne]3s²3p¹
(b) [Ne]3s²3p³
(c) [Ne]3s²3p²
(d) [Ar]3d¹⁰4s²4p³
Sol: (b) (b) and (d) have exactly half-filled p-orbitals but (b) is smaller in size than Hence, (b) has highest ionization enthalpy.

More than One Correct Answer Type

Q23. Which of the following have identical bond order?
(a) CN^– (b) NO⁺                      (c) 0^–₂                        (d) 0₂^2-
Sol: (a, b) CN^– (number of electrons = 6 + 7 + 1 = 14)
NO⁺ (number of electrons = 7 + 8 – 1 = 14)
0^–₂ (number of electrons = 8 + 8 + 1 = 17)
0₂^2- (number of electrons = 8 + 8 + 2 = 18)
Thus, CN and NO⁺ because of the presence of same number of electrons, have same bond order.

Q24. Which of the following attain the linear structure?
(a) BeCl₂
(b) NCO⁺                  
(c) N0₂                     
(d) CS₂
Sol: (a, d) BeCl₂ (Cl – Be – Cl) and CS₂ (S = C = S) both are linear, NCO⁺ is non-linear. However, remember that NCO(N = C = O) is linear because it is isoelectronic with C0₂.
N0₂ is angular with bond angled 132° and each O – N bond length of 1.20A^o (intermediate between single and double bond).

Q25. CO is isoelectronic with
(a) NO⁺
(b) N₂                       
(c) SnCl₂                  
(d) N0₂
Sol: (a, b) Number of electrons in CO =14
Number of electrons in NO⁺ =14
Number of electrons in N₂ = 14
Number of electrons in SnCl₂ = 84
Number of electrons in N0^–₂ = 24

Q26. Which of the following species have the same shape?
(a) C0₂
(b) CC1₄                 
(c) 0₃                        
(d) N0^–₂
Sol: (c, d) C0₂ →Linear, CC1₄ → Tetrahedral, 0₃ →Angular (V-shaped), N0^–₂ →Angular (V-shaped)

Q27. Which of the following statements are correct about CO₃^2- ?
(a) The hybridization of central atom is sp³.
(b) Its resonance structure has one C – O single bond and two C = O double bonds.
(c) The average formal charge on each oxygen atom is 0.67 units.
(d) All C – O bond lengths are equal.

Q28. Diamagnetic species are those which contain no unpaired electrons. Which among the following are diamagnetic?
(a) N₂                     
(b) N₂^2- 
(c) 0₂                      
(d) o₂^2-

Q29. Species having same bond order are
(a) N₂                      
(b) N^–₂                       
(_C) F⁺₂                      
(d) o^–₂

Q30. Which of the following statements are not correct?
(a) NaCl being an ionic compound is a good conductor of electricity in the solid state.
(b) In canonical structures there is a difference in the arrangement of atoms.
(c) Hybrid orbitals form stronger bonds than pure orbitals.
(d) VSEPR theory can explain the square planar geometry of XeF₄.
Sol: (a, b)
(a) Ionic compounds are good conductors only in molten state or aqueous solution since ions are not furnished in solid state.
(b) In canonical structures there is a difference in arrangement of electrons.

Short Answer Type Questions
Q31. Explain the non linear shape of H₂S and non planar shape of PCl₃ using valence shell electron pair repulsion theory.
Sol: The Lewis structure of H₂S is:

Q32. Using molecular orbital theory, compare the bond energy and magnetic character of 0⁺₂ and O^–₂

Q33. Explain the shape of BrF₅.
Sol: Br-atom has configuration:
1s², 2s²2p⁶ , 3s²3p⁶3d¹⁰, 4s²4p⁵
To get pentavalency, two of the p-orbitals are unpaired and electrons are shifted to 4d-orbitals.

In this excited state, sp³d²-hybridisation occurs giving octahedral structure. Five positions are occupied by F atoms forming sigma bonds with hybrid bonds and one position occupied by lone pair, i.e., the molecule as a square pyramidal shape.

Q34. Structures of molecules of two compounds are given below:

(a) Which of the two compounds will have intermolccular hydrogen bonding and which compound is expected to show intramolecular hydrogen bonding?
(b) The melting point of a compound depends on. among other things, the extent of hydrogen bonding. On this basis explain which of the above two compounds will show higher melting point.
(c) Solubility of compounds in water depends on power to form hydrogen bonds with water. Which of the above compounds will form hydrogen bond with water easily and be more soluble in it?
Sol:(a) Compound I will form intramolecular hydrogen bond because N02 and OH groups are close together whereas it is not so in compound II. Compound II will have intermolecular hydrogen bonding. Bonding in both the cases is shown below:

(b) As a large number of molecules can be linked together through intermo­lecular hydrogen bonding, compound II will show higher melting point.

(c) Due to intramolecular hydrogen bonding, compound I will not be able to form hydrogen bonds with H₂0 molecules. Hence, it will be less soluble in water. However, compound II can form hydrogen bonds with H₂0 molecules easily and hence it will be more soluble in water.

Q35. Why does type of overlap given in the following figure not result in the bond formation?

Sol: In first figure, the ++ overlap is equal to +- overlap and therefore, these cancel out and net overlap is zero.
In second figure, no overlap is possible because the two orbitals are perpendicular to each other.

Q36. Explain why PC1₅ is trigonal bipyramidal whereas IF₅ is square pyramidal.
Sol: PC1₅ – The ground state and the excited state outer electronic configurations of phosphorus (Z = 15) are represented below

Sol: Dimethyl ether has larger bond angle than water. This is because there is more repulsion between bond pairs of CH₃ groups attached in ether than between bond pairs of hydrogen atoms attached to oxygen in water. The carbon of CH₃ group in ether is attached to three hydrogen atoms through c bonds and electron pairs of these bonds add to the electron charge density on carbon atom. Hence, repulsion between two -CH₃ groups will be more than that between two H atoms.

Q38. Write Lewis structure of the following compounds and show formal charge on each atom. HN0₃, No₂, H₂so₄
Sol: Formal charge on an atom in a Lewis structure
= [total number of valence electrons in free atom] – [total number of non-bonding (lone pairs) electrons]
—1/2 [total number of bonding or shared electrons]

Q39. The energy of σ2p_z: molecular orbital is greater than 2p_x and 2p_v molecular orbitals in nitrogen molecule. Write the complete sequence of energy levels in the increasing order of energy in the molecule. Compare the relative stability and the magnetic behaviour of the following species:
N₂, N⁺₂, N^–₂, N²₂⁺

Q40. What is the effect of the following processes on the bond order in N-, and 0₂?
(i) N₂ → N⁺₂ + e^– (ii) 0₂ → O⁺₂ + e^–

Q41. Give reasons for the following: ‘
(a) Covalent bonds are directional bonds while ionic bonds are non- directional.
(b) Water molecule has bent structure whereas carbon dioxide molecule is linear.
(c) Ethyne molecule is linear.
Sol: (i) Since the covalent bond depends on the overlapping of orbitals between different orbitals, the geometry of the molecule is different. The orientation of overlap is different. The orientation of overlap is the factor responsible for their directional nature.
(ii) Due to presence of two lone pairs of electrons on oxygen atom in HiO the repulsion between Ip-lp is more. C0₂ undergoes sp hybridization resulting in linear shape (O = C = O) while H₂0 undergoes .sp³ hybridisation resulting in distorted tetrahedral or bent structure.

(iii) In ethyne molecule carbon undergoes sp hybridization with two unhybridised orbitals. One sp hybrid orbital of one carbon atom overlaps axially with sp hybrid orbital of the other carbon atom to form C – C sigma bond while the other hybridized orbital of each carbon atom overlaps axially with S orbitals of hydrogen atoms forming σ bonds. Unhybridised orbitals form π bonds

Q42. What is an ionic bond? With two suitable examples explain the difference between an ionic and covalent bond?
Sol: An ionic bond is formed as a result of the electrostatic attraction between the positive and negative ions formed by transfer of electrons from one atom to another.

Q43. Arrange the following bonds ‘in order of increasing ionic character giving reason.
N-H, F-H, C-H and O-H

Sol. Electronegativity difference

Increasing order of electronegativity difference: C-H<N-H<0-H<F-H
Greater is the difference in electronegativity between two bonded atoms, greater is the ionic character.

Q44. Explain why CO^2-₃ ion cannot be represented by a single Lewis structure. How can it be best represented?
Sol: A single Lewis structure of CO^2-₃  ion cannot explain all the properties of this ion. It can be represented as a resonance hybrid of the following structures:

If it were represented only by one structure, there should be two types of bonds, i.e., C = O double bond and C – O single bonds but actually all bonds are found to be identical with same bond length and same bond strength.

Q45. Predict the hybridization of each carbon in the molecule of organic compound given below. Also indicate the total number of sigma and pi bonds in this molecule.

Q46. Group the following in linear and non-linear molecules: H₂0, HOC1, BeCl₂ C1₂0

Q47. Elements X, Y and Z have 4, 5 and 7 valence electrons respectively, (i) Write the molecular formula of the compounds formed by these elements individually with hydrogen, (ii) Which of these compounds will have the highest dipole moment?

Q48. Draw the resonating structure of (i) Ozone molecule (ii) Nitrate ion

Q49. Predict the shapes of the following molecules on the basis of hybridization. BC1₃, ch₄, co₂, nh₃
Sol: BCl₃ – sp² hybridisation – Trigonal planar
CH₄ – sp³ hybridisation – Tetrahedral .
NH₃ – sp³ hybridisation – Distorted tetrahedral or Pyramidal

Q50. All the C – O bonds in carbonate ion (CO^2-₃) are equal in length. Explain.
Sol: Carbonate ion is represented by resonating structures as given below:

Q51. What is meant by the term average bond enthalpy? Why there is difference in bond enthalpy of O – H bond in ethanol (C₂H₅OH) and water?

Matching Column Type Questions
Q52. Match the species in Column I with the type of hybrid orbitals in Column II.

Q53. Match the species in Column I with the geometry/shape in Column II.

Q54.  Match the species in Column I with the bond order in Column II.

Q55. Match the items given in Column I with examples given in Column II.

Q56. Match the shape of molecules in Column I with the type of hybridization in Column II.

Sol: (i) →c; (ii) → a; (iii) —> b

sp³ hybridisation – Tetrahedralshape
sp² hybridisation – Trigonal shape
sp hybridization – Linear shape

Assertion and Reason Type Questions

In the following questions a statement of Assertion (A) followed by a statement of Reason (R) is given. Choose the correct option out of the choices given below each question.

Q57. Assertion (A): Sodium chloride formed by the action of chlorine gas on sodium metal is a stable compound.
Reason (R): This is because sodium and chloride ions acquire octet in sodium chloride formation.
(a) A and R both are correct, and R is the correct explanation of A.
(b) A and R both are correct, but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A and R both are false.
Sol: (a) Sodium chloride (Na⁺CL^–) is stable ionic compound because both Na⁺ and CL^– ions have complete octet in outermost shell.

Q58. Assertion (A): Though the central atom of both NH₃ and H₂0 molecules are sp³ hybridised, yet H – N – H bond angle is greater than that of H – O – H.
Reason (R): This is because nitrogen atom has one lone pair and oxygen atom has two lone pairs.
(a) A and R both are correct, and R is the correct explanation of A.
(b) A and R both are correct, but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A and R both are false.

Sol:(a)

H₂0 has two lone pairs while NH₃ has single lone pair, hence, H₂0 involves greater lone pair-bond pair repulsion.

Q59. Assertion (A): Among the two O – H bonds in H₂0 molecule, the energy required to break the first O – H bond and other O – H bond is the same.
Reason (R): This is because the electronic environment around oxygen is the same even after breakage of one O – H bond.
(a) A and R both are correct, and R is the correct explanation of A.
(b) A and R both are correct, but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A and R both are false.
Sol: (d) Bond energy of two (-O – H) bonds in H₂0 will be different.

Long Answer Type Questions
Q60. (i) Discuss the significance/applications of dipole moment.
(ii) Represent diagrammatically the bond moments and the resultant dipole moment in C0₂, NF₃ and CHCl₃.

Sol: (i) Dipole moment plays very important role in understanding the nature of chemical bond. A few applications are given below:
(a) Distinction between, polar and non-polar molecules. The measurement of dipole moment can help us to distinguish between polar and non-polar molecules. Non-polar molecules have zero dipole
moment while polar molecules have some value of dipole moment.
(b) Degree of polarity in a molecule. Dipole moment measurement also gives an idea about the degree of polarity specially in a diatomic molecule. The greater the dipole moment, the greater is the polarity in such a molecule.
(c) Shape of molecules. In case of molecules containing more than two atoms, the dipole moment not only depends upon the individual dipole moments of the bonds but also on the arrangement of bonds.
.Thus, dipole moment is used to find the shapes of molecules.
(d) Ionic character in a molecule. Knowing the electronegativities of atoms involved in a molecule, it is possible to predict the nature of chemical bond formed. If the difference in electronegativities of two atoms is large, the bond will be highly polar. As an extreme case, when the electron is completely transferred from one atom to another, an ionic bond is formed. Therefore, the ionic bond is regarded as an extreme case of covalent bond. The greater the difference in electronegativities of the bonded atoms, the higher is the ionic character
(e) Distinguish between cis- and trans- isomers. Dipole moment measurements help to distinguish between cis- and trans- isomers because ds-isomer has usually higher dipole moment than trans isomer.
(f) Distinguish between ortho, meta and para isomers. Dipole moment measurements help to distinguish between o-, m- and p-isomers because the dipole moment of p-isomer is zero and that of o-isomers is more than that of m-isomer.

Q61. Use the molecular orbital energy level diagram to show that N₂ would be expected to have a triple bond, F₂ a single bond and Ne₂ no bond.

No bond is formed between two Ne atoms or in other words, Ne₂ does not exist.
Bond Order = ½ (10 – 10) = 0 (No bond)

Q62. Briefly describe the valence bond theory of covalent bond formation by taking an example of hydrogen. How can you interpret energy changes taking place in the formation of dihydrogen?
Sol: The valence bond theory was put forward by Heitler and London in 1927. It was later improved and developed by L. Pauling and J.C. Slater in 1931. The valence bond theory is based on the knowledge of atomic orbitals and electronic configurations of elements, overlap criteria of atomic orbitals and stability of molecule.
The main points of valence bond theory are
(i) Atoms do not lose their identity even after the formation of the molecule.
(ii) The bond is formed due to the interaction of only the valence electrons as the two atoms come close to each other. The inner electrons do not participate in the bond formation.
(iii) During the formation of bond, only the valence electrons from each bonded atom lose their identity. The other electrons remain unaffected.
(iv) The stability of bond is accounted by the fact that the formation of bond is accompanied by release of energy. The molecule has minimum energy at a certain distance between the atoms known as intemuclear distance. Larger the decrease in energy, stronger will be the bond formed.

Valence bond Treatment of Hydrogen Molecule:
Consider two hydrogen atoms A and B approaching each other havingnuclei H_a and H_B and the corresponding electrons e_A and e_B respectively.
When atoms come closer to form molecules new forces begin to operate.
(a) The force of attraction between nucleus of atom and electron of another atom.
(b) The force of repulsion between two nuclei of the atom and electron of two atoms.

Fig. (a) Two hydrogen atoms at a large distance and hence, no interaction, (b) Two hydrogen atom closer to each other atomic orbitals begin to interact, (c) Attractive and repulsive forces in hydrogen atoms when interaction begins. In case of hydrogen: Figure ‘a’ shows that two hydrogen atoms are at farthest distances and their electron distribution is absolutely symmetrical.
(a) When two hydrogen atom start coming closer to each other, the electron cloud becomes distorted and new attractive and repulsive forces begin to operate as shown in figure ‘c’
(b) In figure ‘c’ dotted lines show attractive forces present in atom already and bold lines show the new attractive and repulsive forces.
(c) It has been found experimentally that the magnitude of net attractive forces is more than net repulsive forces. Thus stable hydrogen molecule is formed.

Potential energy diagram for formation of hydrogen molecules:
When two hydrogen atoms are at farther distance, there is no force operating between them, when they start coming closer to each other, force of attraction comes into play and their potential energy starts decreasing. As they come closer to each other potential goes on decreasing, but a point is reached, when potential energy acquires minimum value.
Note:
(a) This distance corresponding to this minimum energy value is called the distance of maximum possible approach, i.e. the point which corresponds to minimum energy and maximum stability.
(b) If atoms come further closer than this distance of maximum possible approach, then potential energy starts increasing and force of repulsion comes into play and molecules starts becoming unstable.

NCERT Exemplar Problems Class 11 Chemistry

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Environment Sustainable Development – CBSE Notes for Class 11 Indian Economic Development

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The economic development we have achieved so far is on the cost of environmental degradation. The era of globlisation promises higher economic growth, but on the same side it had adverse consequences that had impacted environment.
In order to understand the sustainable path of development, the significance and contribution of environment to economic development should be understood. With this in mind, we would be able to achieve sustainable development in India.

Environment is defined as the total planetary inheritance and the totality of all resources. It includes all the biotic (e.g. birds, animals, plants, forests, etc) and abiotic (e.g., water, Sun, land, mountains, etc) factors that influence each other.
According to the Environment Act-1986, ‘Environment includes, water, air and land and the inter relationship which exists among and between water, air, land and human beings and other creatures, plants, micro organisms and property’.
Functions of Environment
Environment performs four vital junctions, which are as follows
1. Supply Resources
Resources include both renewable and non-renewable sources of energy. Resources which can be used without any fear of getting depleted are renewable sources of energy, e.g. trees, fishes, etc. Non-renewable sources are those which are getting depleted or exhausted. e.g. fossil fuel, etc.
2. Assimilates Waste
Production and consumption activity generates wastes. It is generally in form of garbage which is absorbed by the environment.
3. Sustains Life
Sun, soil, air, water are the essential ingredients of environment for the human life. Absence of these will lead to an end of life on the Earth.
4. Aesthetic Services
Environment provides aesthetic services like scenery, which includes rivers, ocean, mountains and deserts. Enjoying these surroundings adds to the quality of life.
Environmental Crisis
The environment is performing its functions without any interruption as long as the demand of these functions is within its carrying capacity. This means that if the rate of extraction of resources will be above the rate of their regeneration, the environment will fail to perform its functions.
Resources are becoming extinct and wastes are generated beyond the absorptive capacity of the environment. All this has lead to the environmental crisis, it refers to ecological crisis that occurs when the environment of a species or a population changes and destabalises its survival.
Consequence of Environmental Crisis
The points given below describe the consequences of environmental crisis
(i) Development has polluted and dried up rivers and other aquifers, which was deteriorated the quality of water.
(ii) Intensive and extensive excavation of both renewable and non-renewable resources has exhausted some of the vital resources, compelling to spend a huge amount of money on technology and research to explore new resources.
(iii) Decline in air and water quality have resulted in increased number of respiratory and water borne diseases i.e., expenditure of health care is also rising according to a data 70% of water of . India is polluted which cannot be used for drinking purpose.
Global Environmental Issues
The environmental issues which affect the whole world are called global environmental issues such as global warming and ozone depletion. These issues also contribute to increased financial commitments for the government.
These issues are discussed below
1. Global Warming
The gradual increase in the average temperature of Earth’s lower atmosphere is called global warming.
Causes/Effects
It occurs due to greenhouse gases (carbon dioxide, methane and other gases which have the capacity to absorb heat) through burning of fossil fuels (coal and petroleum) and deforestation (increases the carbon dioxide level in atmosphere). Much of the recent observed and projected global warming is human induced.
The atmospheric concentrations of carbon dioxide and methane have increased by 31% and 149% respectively above pre-industrial level since 1750.
Different effects of global warming are described below
(i) During the past century, the atmospheric temperature has risen by 1.10° F (0.60° C).
(ii) Melting of polar ice resulting in increase in sea level (during the past century, sea level has risen by several inches) and the risk of coastal flooding has increased.
(iii) Disruption of drinking water supplies dependent of snow melts.
(iv) Extinction of species.
(v) More frequent tropical storms.
(vi) Increased incidence of tropical diseases.
Action Taken
A United Nations Conference on Climate Change, held in Tokyo, Japan, in 1997, resulted in an international agreement to fight global warming which called for reductions in emissions of greenhouse gases by industrialised nations.
2. Ozone Depletion
It refers to the phenomenon of reductions in the amount of ozone layer in the stratosphere.
Causes/Effects
It is caused by high levels of chlorine and bromine compounds in the stratosphere. Origin of these compounds are Chloro flurocarbons (CFCs), used as cooling substances in air conditioners and refrigerators or as aerosol propellants and bromofluro-carbons.(halons) used in fire extinguishers.
Different effects of ozone depletion are described below
(i) More ultraviolet radiation comes to Earth causing damage to living organisms, skin cancer in humans, low production of phytopjankton affecting acquatic organisms.
(ii) Influences the growth of terrestrial plants.
Action Taken
Between 1979 to 1990, a reduction of 5% in ozone layer was detected. Since ozone layer prevents most harmful ultraviolet radiation from passing through the Earth’s atmosphere, so reduction in ozone layer generated worldwide concern, leading to adoption of the montreal protocol banning the use of Chloroflurocarbon JCFC) compounds as well as other ozone depleting chemicals such as carbon tetrachloride, tricholoroethane (also known as methyl chloroform) and bromine compounds known as halons.
State of India’s Environment
India has rich quality of natural resources in plenty of amount.
It is clear from the following points
(i) India has rich quality of soil, hundreds of rivers and tributaries, lush green forests, plenty of mineral deposits beneath the land surface, vast stretch of the Indian Ocean, ranges of mountains, etc.
(ii) The black soil of the Deccan Plateau is particularly suitable for cultivation of cotton. It has lead to concentration of textile industries in this region.
(iii) The Indo Gangetic plains spread from Arabian Sea to the Bay of Bengal are one of the most-fertile, intensively cultivated and densely populated regions in the world.
(iv) India’s forests though unevenly distributed, provide green cover for majority of its population and natural cover for its wildlife.
(v) Large deposits of iron-ore, coal and natural gas are found in the country. India alone accounts for nearly 20% of the world’s total iron-ore reserves.
(vi) Bauxite, copper, chromate, diamonds, gold, lead, lignite, manganese, zinc, uranium, etc are also available in different parts of the country.
Threat to India’s Environment
Threat to India’s environment is poverty, pollution, rapidly growing industrial sector. Air pollution, water contamination, soil erosion, deforestation and wildlife extinction are some of the most pressing environmental concerns of India. The developmental activities in India have resulted in pressure on its finite natural resources, besides creating impacts on human health and well-being.
Out of them the priority issues are
(i) Land degradation and solid waste management
(ii) Biodiversity loss
(iii) Air pollution with special reference to vehicular pollution in urban cities
(iv) Management of fresh water
Some of these issues are discussed below
Land Degradation in India
Land in India suffers from varying degrees and types of degradation stemming mainly from unstable use and inappropriate management practices.
The factors responsible for land degradation in India are
(i) Loss of vegetation occuring due to deforestation.
(ii) Unsustainable fuel wood and fodder extraction.
(iii) Shifting cultivation.
(iv) Reduction into forest lands.
(v) Forest fifes and overgrazing.
(vi) Non-adoption of adequate soil conservation measures.
(vii) Improper crop rotation.
(viii) Indiscriminate use of agro chemicals
such as fertilisers and pesticides.
(ix) Improper planning and management of irrigation system.
(x) Extraction of ground water in excess of the regain capacity.
(xi) Open access resource.
(xii) Poverty of the agriculture-dependent people.
Biodiversity Loss
India is the owner of 2.5% of world’s geographical area. India holds 17% of human and 20% of livestock population on its land. In order to hold livestock and human in country, country needs 0.47 hectare of land to meet the basic needs but it has only 0.08 hectare of land which causes felling of forests and soil erosion. 5.3 billion tonnes of soil is eroded every year. As a result quantity of nutrients lost due to erosion each year ranges from 5.8 to 8.4 million tonnes.
Chipko or Appiko : What’s in a Name?
Chipko Movement aimed at protecting forests in the Himalayas. In Karnataka, a similar movement took a different name, ‘Chpiko’, which means to hug.
On 8th September 1983, when the felling of trees was.started in Salkani forest in Sirsi district, 160 men, women and children hug|ed the trees and forced the woodcutters to leave. They kept vigil in the forest over the next six weeks. Only after the forest officials assured the volunteers of the trees will be cut scientifically and in accordance with the working plan of the district, did they leave the trees, When commercial felling by contractors damaged a large number of natural forests, the idea of hugging the trees gave the people hope and confidence that they can protect the forests. On that particular incident, with the felling discontinued, the people saved 12000 trees. Within months, this movement spread to many adjoining districts.
Air Pollution
In India, air pollution is widespread in urban areas where vehicles are the major contributors and in a few other areas which have a high concentration of industries and thermal power plants.
Pollution from vehicles and industries are the major sources of air pollution.
(i) Vehicle Pollution Vehicle emissions are of particular concern since these are ground level sources and thus, have the maximum impact on the general pollution. The number of vehicles has increased from 3 lakh in 1957 to 67 crores in 2003.
In 2003, personal transport vehicles (two wheeled and cars only) contributed about 80% of the total number of registered vehicles thus, contributing significantly to air pollution load.
(ii) Industrial Pollution India is one of the ten most industrialised nations of the world. This status has brought with it unwanted and unanticipated consequences like unplanned urbanisation, pollution and the risk of accidents.
The CPCB (Central Pollution Control Board) has identified seventeen categories of industries (large and medium scale) as significantly polluting.
Management of Fresh Water
Water is an equally important element of life and its pollution is equally serious. Water becomes polluted when chemicals and other waste materials are dumped into it. Polluted water is the principal cause of diseases like diarrhoea and hepatitis. Thus, the management of fresh water is essential to sustain life.
Pollution Control Boards
To address two major environmental concerns in India; water, air and land pollution, the government set up the Central Pollution Control Board (CPCB) in 1974. This was followed by states establishing their own state level boards to address all the environmental concerns.
Different functions of pollution control boards are
(i) To investigate, collect and disseminate information relating to water, air and land pollution.
(ii) To lay down standards for sewage/trade effluent and emissions.
(iii) To provide technical assistance to governments in promoting cleanliness of streams and wells by prevention, control and abatement of water pollution.
(iv) To improve the quality of air and to prevent, control or abate air pollution in the country.
(v) To carryout and sponsor investigation and research relating to problems of water and air pollution and for their prevention, control and abatement.
(vi) To organise mass awareness programme for pollution control.
(vii) To prepare manual, codes and guidelines relating to treatment and disposal of sewage and trade effluents.
(viii) To assess the air quality through regulation of industries.
(ix) State boards through their district officials, periodically inspect every industry under their jurisdiction to assess the adequacy of treatment measures provided to treat the effluent and gaseous emissions.
(x) State pollution boards also provide background air quality data needed for industrial siting and town planning.
In nutshell, it can be said that pollution control boards collect, collate and disseminate technical and statistical data relating to water pollution. They monitor the quality of water in 125 rivers (including the tribunaries), wells, lakes, ponds, tanks, drains and canals.
How to Save Environment?
The various measures adopted by Ministry of Environment and the central and state pollution control boards may not yield reward unless, we make ourself concious.
Following are required measures which should be taken to save the environment
(i) Social Awareness There should be awareness among the people regarding the threats of the increasing pollution and how can each of us contribute to the check this menace.
(ii) Population Control Biggest issue which should be controlled is increasing population to protect the environment.
(iii) Enforcement of Environment Conservation Act
The Environment act was passed in year 1986. It was passed to check the detoriated quality of the environment.
(iv) Afforestation Campaign Extensive afforestation campaign should be launched to protect environment.
(v) Water Management There should be means which can harvest the rain water in order to use it in the areas where there is scarcity of water, so that clean drinking water can be provided to the rural people.
(vi) Management of Solid Waste Management of solid waste is very essential. It should be treated chemically. Rural garbage should be converted into compost.

Meaning, Features, Needs and Strategies for Sustainable Development

According to the United Nations Conference on Environment and Development (UNCED), sustainable development can be defined as “development strategy that meets the need of present generation without compromising the ability of future generation to meet their own needs.”
Edward Barbier, a renowned personality had also given the definition of sustainable development Sustainable development is one which is directly concerned with increasing the material standards of living of the poor at grass root level.
In specific term, sustainable development aims at decreasing the absolute poverty of the poor by providing lasting and securing livelihoods that minimise resource depletion, environmental degradation, cultural disruption and social instability.
The Brudtland Commission emphasises on protecting the future generation. A moral obligation to hand over the planet Earth in good order to the future generation, i. e., the present generation should bequeath a better environment to the future generation.
The present generation can promote development that enhances the natural and built environment in the way, that are compatible with
(i) conservation of natural as us.
(ii) preservation of the regenerative capacity of the worlds natural ecological system.
(iii) avoiding the imposition of added costs or risks on future generation.
Features of Sustainable Development
(i) Sustained rise in real per capital income and economic welfare.
(ii) Rational use of natural resources.
(iii) No reduction in the ability of future generations to meet their own needs.
(iv) Check on pollution.
A Way to Sustainable Development
According to Herman Dalay, a leading environmental economist, the main needs of sustainable development are
(i) Limiting the human population to a level within the carrying capacity of the environment.
(ii) Technological progress should be input efficient and not input consuming.
(iii) Renewable resources should be extracted on a sustainable basis, i.e., rate of extraction should not exceed rate of regeneration.
(iv) For non-renewable resources, rate of depletion should not exceed the rate of creation of renewable substitutes.
(v) Inefficiencies arising from pollution should be corrected.
Strategies for Sustainable Development
1. Use of Non-conventional Sources of Energy
India heavily depends on thermal and hydro power plants to meet its power needs. Both of these have adverse environmental impacts. Thermal power plants emit large quantities of carbon dioxide, which is a greenhouse gas. If it is not used properly, it may cause land and water pollution.
2. LPG, Gobar Gas in Rural Areas
Rural households in India generally use wood, dungcake (upla) or other biomass as fuel. This practice has several adverse implications like deforestation, reduction in green cover and air pollution.
To rectify the situation, subsidised LPG is being provided. Besides it, gobar gas plants are being encouraged through easy loans and subsidy. LPG is the clean fuel. It does not create any household pollution and also wastage is minimised. For gobar gas plants, cattle dung is fed in the plant to function which produces gas and slurry is used as organic soil fertiliser.
3. CNG in Urban Areas
In Delhi, the use of Compressed Natural Gas (CNG) as fuel in public transport system has significantly lowered air pollution and the air has become cleaner in the last few years.
4. Wind Power
In areas, where speed of wind is usually high, wind mills can provide electricity without any adverse impact on the environment. The turbines moves with wind and electricity gets generated. Its initial cost’ remain high but it can be recovered easily.
5. Solar Power Through Photovoltaic Cells
In India, solar energy is used in different forms for agriculture products, daily use products and even to warm ourselves in winters. Through photovoltaic cells, solar energy can be converted into electricity. This technology is extremely useful for remote areas and for places where supply of power lines is either not possible or proves very costly. This technique is also totally free from pollution.
6. Bio Composting
In order to increase production, we have started using chemical fertilisers which are adversely affecting the waterbodies, ground water system, etc. But again farmers in large numbers have started using organic fertilisers for production.
In some parts, cattles are maintained only because their waste prouction is very useful in form of fertiliser. Earthworm can convert organic matter into compost faster than the normal composting process.
7. Mini-Hydel Plants
Mountainous regions have streams every where. Most of such streams are perennial. Mini-hydel plants use the energy of such streams to move small turbines which generate electricity. Such power plants are more or less environment friendly.
8. Traditional Knowledge and Practices
Traditionally, Indian people have been close to their environment. If we look back at our agriculture system, healthcare system, housing, transport, etc we find that all practices have been environment friendly. But in recent years, we have been moving away from these practices. This has caused large scale damage to our environment.
During older times, we used Ayurveda, Unani, Tibetan and Folk systems for the treatments but now we are ignoring the traditional system and we are moving towards the western system. Not only these products were environment friendly but they are free from side effects too.
9. Biopest Control
With the advent of Green Revolution, the country entered into the use of chemical pesticides to produce more which laid the adverse impacts on soil, water bodies, milk, meat and fishes. To meet this challenge, better methods of pest control should be brought. One step is pesticides based on plants like neem. Even many animals also help in controlling pests like snakes, peacocks, etc.

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Comparative Development Experience of India with its Neighbours – CBSE Notes for Class 11 Indian Economic Development

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This chapter will not be examined. Open Text Based Assessment (OTBA) will be based on this chapter.
Nations are also eager to know and understand about the developmental process pursued by their neighbouring nations. It allows them to comprehend their strengths and weaknesses. In the process of globalisation, it is essential for every nation to compete with developed countries.
In this chapter, we are comparing the developmental strategies pursued by India with its neighbouring economies-Pakistan and China. This will help in understanding where do we stand today in comparison to others.
Development Strategies of India, China and Pakistan
India, China, Pakistan have many similarities in their development strategies which are as follows
(i) India, Pakistan and China have started towards their developmental path at the same time. India and Pakistan became independent nations in 1947. While Peoples Republic of China was established in 1949.
(ii) All the three countries had started planning their development strategies in similar ways. India announced its Five Year Plan in 1951-56, while ’ Pakistan announced its first Five Year Plan in 1956, which is called Medium Term plan. China announced its First Five Year Plan in 1953.
(iii) India and Pakistan adopted similar strategies such as creating a large public sector and raising public expenditure on social development.
(iv) Till the 1980s, all the three countries had similar growth rates and per capita incomes.
(v) Economic reforms took place in all the three countries. Reforms started in India in 1991, in China in 1978 and in Pakistan in 1988.
Development Strategies of India
Some of the prominent strategies of India are discussed below
1. Sound Trade System
India was a country which had the history of closed trade. Because of this historical background; there is a critical challenge for India in order to make a new policy which can support the new open trade system. This new reform in economies of India has been introduced and accelerates the economic growth of India.
2. Reduction in Poverty
India has adopted several poverty alleviation programmes to reduce poverty in India. -This would help in increasing per capita income, rise in nutrition level of poors and there is a subsequent fall in percentage of absolute poor in some states.
3. Rural Development
Under this strategy, India adopted various measures for the development of areas that are lagging behind in the overall development of village economy.
4. Employment Generation
Several economic reforms were initiated to generate employment in the country and their aim is to provide gainful self-employment and skilled wage employment opportunities.
Development Strategies of China
After the establishment of People’s Republic of China under one party rule, all the critical sectors of the economy, enterprises and lands owned and operated by individuals were brought under government control.
Certain development strategies of China are discussed below
1. Great Leap Forward (GLF)
This campaign initiated in 1958 aimed at industrialising the country on a massive scale. People were encouraged to set up industries in their backyards. In rural areas, communes were started. Under the commune system, people collectively cultivated lands.
2. Great Proletarian Cultural Revolution (1966-76)
In 1965, Mao Tse Tung started a cultural revolution on a large scale. In this revolution, students and professionals were sent to work and learn from the country side. Unlike GLF, the cultural revolution did not have an explicit economic rationale.
3. 1978 Reforms
Since 1978, China began to introduce many reforms in phases. The reforms were initiated in agriculture, foreign trade and investment sector. In agriculture, lands were divided into small plots which were allocated to individual households. They were allowed to keep all income from the land after paying taxes.
In later phase, reforms were initiated in industrial sector. All enterprises which were owned and operated by local collectives in particular, were allowed to produce goods.
At this stage, enterprises owned by government (known as State Board Enterprises – SOEs), in India we call them public sector enterprises were made to face competition. In reform, prices were fixed in two ways, i.e., farmers and industrial units were required to buy and sell fixed quantities of inputs and outputs on the basis of prices fixed by the government and the rest were purchased and sold at market prices.
Over the years, as production increased, the proportion of goods or inputs transacted in the market also increased. The goal of Chinese economic reforms was to generate sufficient surplus to finance the modernisation of the mainland Chinese economy. In order to attract foreign investors, Special Economic Zones (SEZs) were set up.
Development Strategies of Pakistan
The development strategies of Pakistan are summarised below
1- Mixed Economy
Pakistan follows a mixed economy system where both public and private sectors co-existed.
2. Import Substitution
Pakistan adopted a regulatory policy framework in the late 1950s and 1960s for import industrialisation. The -policy combined tariff protection for manufacturing of consumer goods together with direct import controls on competing imports.
3. Green Revolution
This was introduced to increase the productivity and self sufficiency in food. This increased the output* of foodgrains. This had changed the agrarian structure dramatically. In 1970’s nationalisation of capital goods took place. Pakistan shifted its policy orientation in 1970’s and 1980’s when private sector got encouragement.
During this period, Pakistan received financial support from Western. This helped the country in stimulating economic growth. Government also offered incentives to private sector. This had a created climate for new investments. And in 1988 certain reforms were also initiated in the country.
Success and Failure of Strategies
The development strategies brought structural reforms in China, India and Pakistan. Follow the description of their success and failure one by one.
Success of Structural Reforms in China
The success of structural reforms in China are
(i) There was existence of infrastructure in the areas of education and health and land reforms.
(ii) There was decentralised planning and existence of small enterprise.
(iii) Through the commune system, there was more equitable distribution of foodgrains.
(iv) There was extension of basic health services in rural areas.
Failures of Structural Reforms in China
The failures of structural reforms in China are
(i) There was slow pace of growth and lack of modernisation in the Chinese economy under the Maoist rule.
(ii) Maoist vision of economic development based on decentralisation, self sufficiency and shunning of foreign technology had failed.
(iii) Despite of extensive land reforms, collectivisation, the great leap forward and other initiatives, the per capita gain output in 1978 was the same as it was in the mid-1950s.
China has an Edge Over India
The Chinese reform process began more comprehensively during the 80s, when India was in the mid-stream of slow growth process.
Rural poverty in China declined by 85% during the period 1978 to 1989. In India, it declined only by 50% during this period, Global exposure of the economy has been far more wider in China than in India. China’s export-driven manufacturing has recorded on exponential growth, while India continues to be only a marginal player in the international markets.
Common Success of Structural Reforms in India and Pakistan
The common success of structural reforms in India and Pakistan are
(i) Both India and Pakistan have succeeded in more than doubling their per capita incomes inspite of high growth rate of population.
(ii) The incidence of poverty has also been reduced significantly. However, the level of poverty is lower in Pakistan.
(iii) Both the countries have achieved self-sufficiency in the production of food.
(iv) Both the countries have succeeded in developing their service and industry sectors at a fast rate.
(v) The use of modern technology is improving in both the countries.
Common Failures of Structural Reforms in India and Pakistan
The common failures of structural reforms in India and Pakistan are
(i) Growth rate of GDP and its sectoral constituents have fallen in 1990’s.
(ii) Poverty and unemployment are still areas of major concerns in both the countries.
Areas Where Pakistan has an Edge Over India
Starting from almost the same level as India, Pakistan has achieved better results with regards to
(i) Migration of workforce from agriculture to industry,
(ii) Migration of people from rural to urban areas.
(iii) Access to improved water sources.
(iv) Reduction in below poverty line population.
Areas where India has an Edge Over Pakistan
There is little doubt that, in the area of skilled manpower and research and development institutions. India is better placed than Pakistan. Indian scientists excel in the areas of defence technology, space research, electronics and avionics, genetics, telecommunications, etc. The number of Ph.Ds produced by India in science and engineering every year (about 5000) is higher than the entire stock of Ph.Ds in Pakistan. Issues of health facilities in general and infant mortality in particular are better addressed in India.

Comparative Study

With Respect to Demographic Indicators, GDP and HDI .
I. Demographic Indicators
We shall compare some demographic indicators of India, China and Pakistan
(i) The population of Pakistan is very small and accounts for roughly about one-tenth of China or India. Though China is the largest nation and geographically occupies the largest area among the three nations, its density is the lowest.
(ii) One child norm was introduced in China in late 1970’s to check the problem of population growth. This measure led to decline in the sex ratio. Although sex ratio is biased against females in all three countries, in recent times, all three countries are trying to adopt various measures to improve the situation.
After few decades there will be more elderly people in proportion to young people due to one child norm.
(iii) The fertility rate is low in China and very high in Pakistan.
(iv) Urbanisation is high in both Pakistan and China.

II. Gross Domestic Product and Sectors
According to the latest data available, we find
(i) China has the second largest GDP (PPP) of US$ 10.1 trillion whereas, India’s GDP (PPP) is US $ 4.2 trillion and Pakistan’s GDP (PPP) is 0.47 trillion US$; roughly about 10% of India’s GDP.
(ii) In 1980’s, Pakistan was ahead of India, China was having double digit growth and India was at the bottom.

Source Key indicators for Asia and Pacific 2011, Asian Development Bank, Phillipines
(iii) In 2000-10 there is a marginal decline in India and Chinas growth rates whereas Pakistan met with drastic decline in 4.7%. The reform processes introduced in 1988 in Pakistan and political instability are reasons behind this trend.
(iv) China and Pakistan have more proportion of urban people than India.
(v) In China, due to topographic and climatic conditions, the area suitable for cultivation is relatively small-only about 10% of its total land area. The total cultivable area in China accounts for 40% of the cultivable area in India.
(vi) Until the 1980s, more than 80% of the people in China were dependent on farming as their sole source of livelihood.
(vii) The government encouraged people to leave their fields and pursue other activities such as handicrafts, commerce and transport.
(viii) In 2008, with 40% of its workforce engaged in agriculture, its contribution to GDP in China is 10%.

(ix) In both India and Pakistan, the contribution of agriculture to GDP was at 19 and 21% respectively. But the proportion of workforce that works in this sector is more in India. In Pakistan, about 45% of people work in agriculture whereas in India it is 56%.
(x) The sectoral share of output and employment also shows that in all the three economies, the industry and service sectors have less proportion to workforce but contribute more in terms of output.
(xi) In China, manufacturing contributes the highest to GDP at 47% whereas in India and Pakistan, it is the service sector which contributes the highest. In both these countries, service sector accounts for more than 50% of GDP. In the normal course of development, countries first shift their employment and output from agriculture to manufacturing and then to services. This is what, is happening in China.
The proportion of workforce engaged in manufacturing in India and Pakistan were low at 49 and 20% respectively.

(xii) The contribution of industries to GDP is also just equal to or marginally higher than the output from agriculture.
In India and Pakistan, the shift is taking place directly to the service sector.
(xiii) Thus, in both India and Pakistan, the service sector is emerging as a major player of development. It contributes more to GDP and, at the same time, emerges as a prospective employer.
(xiv) In the 1980s India, China and Pakistan employed 17, 12 and 27% of its workforce in the service sector respectively. In 2008-10 it has reached the level of 25, 33 and 35% respectively.
III. Human Development Indicator
India, China and Pakistan have performed in some of the selected indicators of human development.
Some Selected Indicators of Human Development, 2009-10

Source Human Development Report 2011 and World Development Indicators (www.worldbank.org)
From the data we would be able to conclude
(i) China is moving ahead of both India and Pakistan in terms of indicators of human development.
(ii) Pakistan is ahead of India in reducing proportion of people below the poverty line and also its performance in education, sanitation and access to water is better than that of India.
(iii) In China, for one lakh births, only 38 women die whereas, in India 230 women die and in Pakistan 260 women die.
(iv) India is in the worst scenario as compared to the other two countries with respect to access to improved sanitation and clean water.
Human Development Index (HPI)
HDI includes quantitative aspects of per capital, GDP and the quality aspects of performance in. health and education. It is an average of life expectancy index, education index and GDP index.

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How, When and Where – CBSE Notes for Class 8 Social

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Facts that Matter

• History is about the changes that occur over time. It is about the finding out of how things were in the past and how things have changed in the present. As soon as we compare the past with the present we refer to time, we talk of ‘before’ and ‘after’.
• If someone asks you when people began to drink tea or coffee, you would fail to answer this question. It is because people did not begin drinking tea on a one fine day, they developed the taste for it over time. Thus, you can only refer to a span of time, an approximate period over which particular changes became visible.
• Still we have enough reason why we associate history with a string of dates. There was a time when history was an account of battles and big events. It was about rulers and their policies. Historians wrote about the year when a king was crowned, the year he married, the year he fought a particular battle, etc. For such events, specific dates were fixed.
• How do we determine that a particular set of dates is important? The dates we select, the dates around which we compare our story of the past, are not important on their own. They became important because we focus on a particular set of events as important.
• The histories written by British historians in India, the rule of each Governor-General was important. These histories began with the rule of the first Governor-General Warren Hastings and ended with the last Viceroy Lord Mountbatten.
• James Mill was a Scottish economist and political philosopher. In 1817, he wrote a three-volume book, A History of British India. In this he divided Indian history into three periods-Hindu, Muslim and British.
• We divide history into different periods in order to capture the characteristics of a time, its central features as they appear to us. So the terms through we periodise, i.e. demarcate the differences between periods, become important.
• Mill was of the opinion that all Asian societies were of the lower level of civilisations than Europe. According to his telling of history, before the British came to India, Hindu and Muslim despots ruled the country. Religious intolerance and caste taboos dominated the social life of Indian people. British rule, as Mill thought, could civilise India.
• The British were absolutely prejudiced in classifying the Indian history. So the British classification of the Indian history cannot be justified. It is because a variety of faults existed simultaneously along with Hindus and Muslims in these periods.
• Apart from the British classification, historians have divided Indian history into ancient, medieval and modern. This division too has problems. It is a periodisation that is borrowed from the West where the modern period was associated with the growth of all the forces of modernity such as science, reason, democracy, etc. Medieval was the term used to describe a society where these features of modern society did not exist. But the features of modern period were not visible in India during the British rule. Many historians, therefore, refer to this period as colonial.
• The British established their control over India and made it a colony.
• Colonisation is a term that refers to a process in which one country subjugates another and thus brings political, economic, social and cultural changes.
• Historians use different sources in writing about the last 250 years of Indian history. One important source is the official records of the British administration. The British believed that the act of writing was important. Easy instruction, plan, policy, etc. had to be clearly written up. The British also felt that all important documents and letters needed to be carefully preserved. So, they set up record rooms attached to all administrative institutions. Specialised institutions like archives and museums were also set up to preserve important records.
• The practice of surveying also became common under the colonial administration.
• By the early 19th century detailed surveys were being carried out to map the entire country.
• In villages, revenue surveys were conducted.
• From the end of the 19th century, Census operations were held at the interval of every ten years. It prepared all the detailed records of the number of people in all the provinces of India, noting information on castes, religions and occupation.
• All these are official records. These records do not always help us understand what other people in the country felt and what lay behind their actions.
• To know about these things we have diaries of people, accounts of pilgrims and travellers, autobiographies of important personalities, etc.
• All these sources were produced by those who were literate. From these we will not be able to understand how history was experienced and lived by the tribals, and the peasants, the workers in the mines or the poor on the streets.

Words that Matter

• Historian: One who writes about the events of the past, i.e. how things were and how they changed.
• Debate: Discussion on an important topic of public interest.
• Periodisation: Ponding any event into periods.
• Ancient: Very old.
• Medieval: It refers to the period in which features of modem society did not exist.
• Colonization: Colonization is a process in which one country subjugates another and thus brings political, economic, social and cultural changes.
• Subjugation: Gaining control over a country.
• Calligrapher: One who is specialised in the art of beautiful writing.
• Survey: The act of examining and recording the measurements, features etc. of an area of land to prepare a map or plan for it.
• Archives: A place where historical documents or records of a government, an organisation, etc, are stored.
• 1773 — Warren Hastings became the first Governor-General of India.
• 1782 — First map produced by James Rennel.
• 1817 — James Mill published a massive three-volume work, A History of British India.
• 1920s — The National Archives of India came up.

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From Trade to Territory – CBSE Notes for Class 8 Social

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Facts that Matter

• The British power began to emerge in India from the second half of the 18th century.
• The British originally came to India as a small trading company and were reluctant to acquire territories. Ultimately, they became the masters of the vast territory. This did not happen overnight. It took a long time.
• In 1600, the East India Company acquired a Charter from the ruler of England, Queen Elizabeth I, granting it the sole right to trade with the East.
• The royal Charter, however, could not prevent other European powers from entering the eastern markets. The Portuguese established their presence in the western coast of India and got their base in Goa. By the early 17th century, the Dutch too were exploring the possibilities of trade in the Indian Ocean. Soon, the French traders arrived.
• All the companies wanted to buy the same things such as fine qualities of cotton, silk, pepper, cloves, cardamom and cinnamon from the Indian market.
• Competition amongst the companies pushed up the prices at which these goods could be purchased and this reduced the profits that could be earned. The only way the trading companies could flourish was by eliminating rival competitors.
• The first English factory was set up on the banks of the river Hugli in 1651. Soon, the trade expanded and the East India Company persuaded merchants and traders to come and settle near the factory.
• By .1696 it began building^a fort around the settlement. It also bribed Mughal officials into giving the company zamindari rights over three villages. One of these was Kalikata which later became the city of Calcutta or Kolkata as it is now called.
• It also persuaded the Mughal emperor Aurangzeb to issue a farman granting the company the right to trade duty-free.
• The officials of the Company who were carrying on private trade, were expected to pay duty. But they refused to pay which angered the Nawab of Bengal, Murshid Quli Khan. This led to fierce battles.
• After the death of Aurangzeb, the Bengal Nawabs (Murshid Quli Khan, Alivardi Khan and Sirajuddaulah) one after another refused to grant concessions to the Company.
• In such a situation the Company began to think about replacing Sirajuddaulah with a puppet ruler who would willingly give trade concessions and other privileges. They began helping one of Sirajuddaulah’s rivals become the Nawab. Sirajuddaulah got infuriated. This finally led to the Battle of Plassey in which Sirajuddaulah got defeated.
• One of the main reasons for the defeat of the Nawab was that the forces led by Mir Jafar, one of Sirajuddaulah’s commanders, never fought the battle.
• For the Company it was the first victory in India.
• Mir Jafar who had deceived Sirajuddaulah was made the new Nawab of Bengal.
• But Mir Jafar could not prove himself a puppet ruler for a long time. Hence, the Company deposed him and installed Mir Qasirifi in his place. When Mir Qasim complained, he in turn was defeated in the Battle of Buxar in 1764, driven out of Bengal and Mir Jafar was reinstalled, who died the next year, i.e. 1765. In the same year the Mughal emperor appointed the Company as the Diwan of the provinces of Bengal. The Company now began to exploit the vast revenue resources of Bengal.
• After the Battle of Buxar the Company appointed Residents in Indian states. These Residents were political or commercial agents and their job was to serve and further the interests of the company. Through the Residents, the Company began interfering in the internal matters of Indian states. Soon the Company forced the states into a subsidiary alliance. According to the terms of this alliance, Indian rulers were not allowed to have their independent armed forces. They were to be protected by the company, but had to pay for the ‘subsidiary forces’ that the Company was supposed to maintain for the purpose of this protection. If the Indian rulers failed to make the payment, the part of their territory was taken away. Awadh and Hyderabad, for example, were forced to cede territories on this ground.
• Whenever, the Company saw a threat to its political or economic interests, it resorted to direct military confrontation. In this regard we can give example of Mysore.
• Mysore had become powerful under rulers like Haider Ali and his son Tipu Sultan.
• Mysore controlled the profitable trade of the Malabar coast where the company purchased pepper and cardamom. In 1785. Tipu Sultan stopped the export of Sandalwood, pepper and cardamom through the parts of his kingdom, and disallowed local merchants from trading with the Company. This infuriated the Company.
• The Company, for this reason, fought four wars with Mysore. Only in the last the Battle of Seringapatam did the company ultimately win a victory. Tipu Sultan was killed defending his capital Seringapatam.
• The Company also subdued the Marathas in a series of wars.
• From the early 19th century the Company pursued an aggressive policy of territorial expansion.
• Under Governor-General Lord Hastings (1813-1823) a new policy of paramountcy was initiated. The Company now claimed that its authority was paramount or supreme. Following this policy, the Company annexed several states.
• Under Governor-General Lord Dalhousie annexations were at the peak. He devised a policy that came to be known as the Doctrine of Lapse. The doctrine declared that if an Indian ruler died without a male heir his kingdom would become the part of Company territory.
• Satara, Sambalpur, Udaipur, Nagpur and Jhansi were annexed by applying this doctrine.
• In 1856, the Company also took over Awadh.
• When Warren Hastings became the first Governor-General of India he introduced several administrative reforms, especially in the sphere of justice.
• In the early 19th century, the British developed a uniform military culture. Soldiers were increasingly subjected to European-style training, drill and discipline that regulated their life for more than before.
• Thus, the East India Company was transformed from a trading company to a territorial colonial power.

Words that Matter

• Mercantile: The word refers to a business enterprise that makes profit primarily through trade, buying goods cheap and selling them at higher prices.
• Factor: The Company traders were known at that time as factors.
• Farman: A royal order during Mughal period.
• Puppet: The term here is used to refer to a person who is controlled by someone else.
• Negotiation: A formal discussion between people in order to find a solution.
• Charter: An official order or resolution.
• Nabob: The British called the nawab as nabob, who was the symbol of power and authority.
• Subsidiary alliance: As per the terms of this alliance, Indian rulers were not allowed to have their independent armed forces. They were to be protected by the company.
• Injunction: Instruction.
• Subservience: The act of being submissive.
• Confederacy: Alliance.
• Paramountcy: Being paramount or supreme.
• The Doctrine of Lapse: This was a policy of the Company to annex kingdoms. As per this policy if an Indian ruler died without a male heir, his kingdom would become the part of the Company territory.
• Qazi: A judge.
• Mufti: A jurist of the Muslim community responsible for expounding the law that the Qazi would administer.
• Impeachment: A trial by the House of Lords in England on charges of misconduct brought against a person in the House of Commons.
• Sawar: Men on horses.
• Dharmashastra: Sanskrit texts prescribing social rules and codes of behaviour. These were begun to compose from C. 500 BCE onwards.
• Musket: A heavy gun u§ed by infantry soldiers.
• Matchlock: An early type of gun in which the powder was ignited by a match.
• 1498 —Vasco da Gama, a Portuguese explorer, discovered the sea-route to India.
• 1600 —The East India Company acquired a Charter from the ruler of England, Queen Elizabeth I granting it the sole right to trade with the East.
• 1651 —The first English factory was set up on the banks of the river Hugli.
• 1696 —The Company began building a fort around the settlement.
• 1756 —Alivardi Khan died and Sirajuddaulah became the Nawab of Bengal.
• 1757 —The Battle of Plassey took place.
• 1764 —The Battle of Buxar took place.
• 1765 —The Mughal Emperor appointed the Company as the Diwan of the
provinces of Bengal.
• 1782-99 —Tipu Sultan was the ruler of Mysore.

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Ruling the Countryside – CBSE Notes for Class 8 Social

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Facts that Matter

• After the assumption of Diwani in 1765, the Company began to use the vast revenue resources of Bengal. Now the revenues from India could finance company’s expenses. These revenues could be used to purchase cotton and silk textiles in India.
• This caused a huge loss of revenue for Bengal. The Bengal economy fell into deep crisis. Artisans began to desert villages because they were being forced to sell their goods to the Company at low prices. Peasants were also worried. Agriculture cultivation showed signs of collapse. Then in 1770 a terrible famine killed ten million people in Bengal.
• Now the Company felt the need of improvement in the field of agriculture because only then its revenue income was sure.
• Finally, the Company introduced the Permanent Settlement in 1793. The rajas and talukdars were asked to collect rent from the peasants and pay revenue to the Company. The amount to be paid was fixed permanently.
• It was felt that this would ensure a regular flow of revenue into the Company’s treasury and at the same time encourage the zamindars to invest in improving the land.
• But the zamindars were not capable of investing in the improvement of land. The revenue that had been fixed was so high that they found it difficult to pay.
• By the first decade of the 19th century, the prices in the market rose and cultivation slowly expanded. This meant an increase in the income of the zamindars but no gain for the Company since it could not increase a revenue demand that had been fixed permanently.
• The Permanent Settlement was oppressive for the cultivators. The rent they paid to the zamindars was high and their right on the land was insecure.
• Finding the Permanent settlement a failure, Holt Mackenzie, an Englishman, devised a new system called Mahalwari Settlement which came into effect in 1822. The collectors were asked to visit villages, inspect the land, measure the fields and record the customs and right of different groups. The estimated revenue of each plot within a village was added up to calculate the revenue that each village or mahal had to pay. This demand was to be revised periodically.
• In the British territories in the south ryotwar (or ryotwari) system was devised. It was initiated by Captain Alexander Read and developed by.Shomas Munro. This system was gradually extended all over South India.
• The Ryotwari Settlement was made directly with the cultivators (ryots).
• All the new systems proved to be failure. The Company had imposed these systems in order to increase the income from land, but its purpose was not solved becuase the revenue demand was very high.
• By the late 18th century the Company was trying to expand the cultivation of opium and indigo.
• Indian indigo was in great demand in Europe. Hence, the Company in India looked for ways to expand the area under indigo cultivation.
• From the last decades of the 18th century Bengal indigo came to dominate the world market. In 1788 only about 30% of the indigo imported into Britain was from India. By 1810 the proportion had gone up to 95%.
• As the indigo trade grew, commercial agents and officials of the Company began investing in indigo production.
• Indigo cultivation was done under two systems known as nij and ryoti. Within the system of nij cultivation, the planter produced indigo in lands that he directly controlled.
• But it was difficult for planters to expand the area under nij cultivation.
• Indigo could be cultivated only on fertile lands and these were all already densely populated.
• Labour was also not easily available.
• Ni cultivation on a large scale also required several ploughs and bullocks. Investing on purchase and maintenance of ploughs was a big problem. Therefore, planters showed reluctance towards expanding the area under nij cultivation.
• Under the ryoti system, planters forced the ryots to sign a contract, an agreement, also known as satta. Those who signed the contract got cash advances from the planters at low rates of interest to produce indigo. But this system was not in favour of the cultivators because they were not given fair prices after the harvest was ready. Thus, indigo cultivators were highly dissatisfied.
• Several ryots in Bengal refused to grow indigo. Soon they became violent. They got support of the local zamindars and village headmen in their rebellion against the planters.
• This worried the government. It brought in the military to protect the planters and set up the Indigo Commission to enquire into the system of indigo production.
• The Commission held the planters guilty.
• It declared that indigo production was not profitable for ryots. Hence, they were not needed to produce indi§o in future.
• Ultimately indigo production collapsed in Bengal. The planters then shifted their operation to Bihar.

Words that Matter

• Countryside: Rural areas.
• Permanent Settlement: Under this settlement it was decided that the rates of revenues once fixed would not be changed.
• Mahal: In British revenue records mahal is a revenue estate which may be a village or a group of villages.
• Mahalwari Settlement: Under this system the rates of revenues were to be revised periodically, not permanently fixed.
• Ryoti: Cultivator.
• Indigo: A plant that produces rich blue colour.
• Plantations: A large farm operated by a planter employing various forms of forced labour. Plantations are associated with the production of coffee, sugarcane, tobacco, tea and cotton.
• Woad: A plant that produces violet and blue dyes.
• Slave: A person who is owned by someone else, i.e., the slave owner. A slave enjoys no freedom and is compelled to work for the master.
• Bigha: A unit of measurement of land.

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 Tribals, Dikus and the Vision of a Golden Age – CBSE Notes for Class 8 Social

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Facts that Matter

• The customs and rituals of tribal societies differ from those laid down by the Brahmans. Unlike the caste societies, the societies of tribals did not have the sharp social divisions. Those who belonged to the same tribe shared common ties of kinship. But, this did not mean that there were no social and economic differences within tribes.
• By the 19th century, tribal people in different parts of India were involved in a variety of activities.
• Some tribal people engaged in jhum or shifting cultivation. In this type of cultivation, small patches of land were made cleared off trees. The cultivators burnt the vegetation and spread the ash from the firing, which contained potash to fertilise the soil. They used equipments like axe and hoe for preparing the soil for cultivation. They did not plough the land and sow the seeds. Instead they used to scatter the seeds on the field. Once the crop was ready and harvested, they moved to another field.
• Shifting cultivators were found in the hilly and forested tracts of north-east and central India.
• Some tribal groups earned their livelihood by hunting animals and gathering forest produce. They saw forests as essential for survival. The Khonds were such community living in the forests of Orissa. They ate fruits and roots collected from the forest. They used many forest shrubs and herbs for medicinal purposes and sold forest produce in the local markets.
• At times they exchanged goods—getting what they needed in return for their forest produce. Some of them were engaged in some odd jobs in villages such as carrying loads or building roads, etc.
• But a time came when supplies of produce shrank. As a result, more and more tribal people began to wander around in search of work.
• However, Baigas remained in the forest. They did not go anywhere.
• Several tribal groups were engaged in heeding and rearing animals. They were pastoralists who moved with their herds of cattle or sheep according to the seasons. The Van Gujjars of the Punjab hills and the Labadis of Andhra Pradesh were cattle herders, the Gaddis of Kulu were shepherds and the Bakarwals of Kashmir reared goats.
• Many tribal groups preferred to settle down instead of moving from one place to another. They began to use plough, and gradually got rights over the land they lived on.
• The British officials found the settled tribal groups like the Gonds and Santhals more civilised than hunter-gatherers or shifting cultivators.
• The British rule, however, changed the life of the tribal people.
• The tribal chiefs were considered important people because it is they who controlled
their territories. Under the British rule they lost their administrative power and were forced to follow law made by British officials in India.
• The British never liked those tribal groups who moved about and did not have a fixed home. They wanted these tribal groups to settle down. Settled peasants were easier to control and administer than people who were always on move.
• The British also wanted a regular revenue income for the state. Hence, they introduced land settlements—that is, they measured the land, defined the rights of each individual of that land and fixed the revenue demand for the state.
• The British effort to settle jhum cultivators was not very successful.
• The British brought several changes in forest laws. This affected the tribal lives. The British extended their control over all forests and declared that forests were state property. Some forests were classified as Reserved Forests for they produced timber which the British wanted. In these forests people were not allowed to move freely and practise jhum cultivation. As a result, several jhum cultivators moved to other areas.
• Now, the British faced a problem of shortage of labour. Hence, they decided that they would give jhum cultivators small patches of land in the forests and allow them to cultivate these on the condition that those who lived in the villages would have to provide labour to the Forest Department. After this forest villages were established around the Forest Department.
• Many tribal groups reacted against the colonial forest laws.
• During the 19th century, traders and moneylenders began to come into the forests. They offered cash loan to the tribal people and asked them to work for wages.
• The case of the silk growers is worth-mentioning in this regard. In the 18th century, Indian silk was in great demand in European markets. Hence, the East India Company officials tried to encourage silk production to meet the growing demand.
• The Santhals of Hazaribagh reared cocoons. The silk traders sent in their agents who gave loans to them to collect the cocoons. The growers were paid three to four rupees for a thousand cocoons. These were then exported to Burdwan or Gaya where they were sold at five times the price. Thus, the silk-growers earned very little.
• The plight of the tribals ^ho had to go far away from their homes for work was even worse.
• Finally, the tribal groups in different parts of the country rebelled against the changes in laws, the restrictions on their practices, the exploitation by traders and moneylenders, etc. The movement that Birsa Munda led is worth-mentioning here.
• Birsa Munda himself declared that God had appointed him to save his people from trouble, free them from the slavery of dikus (outsiders). Soon, thousands became the followers of Birsa. They all were unhappy with the changes they were experiencing and the problems they were facing under British rule. They wanted to recover their golden past.
• A movement began under the leadership of Birsa Munda. The political aim of the Birsa Movement was to drive out missionaries, moneylenders, Hindu landlords and the government and to set up a Munda Raj with Birsa at its head.
• As the movement spread, the British officials arrested Birsa in 1895.
• In 1897, he was released. Afterwards, he toured the villages to gather support. He urged people to destroy ‘Ravana’ (dikus and the Europeans) and establish a kingdom under his leadership.
• Birsa died in 1900 and the movement initiated by him faded out, but its significance cannot be undermined.

Words that Matter

• Dikus: Outsiders or foreigners
• Jhum Cultivation: In this type of cultivation, the cultivators clear off a patch of land, burn the vegetation and spread the ash from the firing, which contains potash to fertilise the soil. Then they prepare the soil for cultivation. They scatter the seeds on the field. Once the crop is ready they move to another land.
• Fallow: A field left uncultivated for a while so that the soil recovers fertility.
• Mahua: A flower that is eaten or used to make alcohol.
• Bewar: It is a term used in Madhya Pradesh for shifting cultivation.
• Sleeper: The horizontal planks of wood on which railway lines are laid.
• Akhara: Wrestling ground
• Sirdars: Leaders
• Vaishnav: Worshippers of Vishnu
• Satyug: The age of truth

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 Colonialism and the City – CBSE Notes for Class 8 Social

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Facts that Matter:

• In most parts of the western world modern cities grew with industrialisation. In Britain industrial towns like Leeds and Manchester grew rapidly in the 19th and 20th centuries.
• In India Calcutta, Bombay and Madras emerged in importance as Presidency cities in the late 18th century.
• These Presidency cities became the centre of British power in the different regions of India.
• At the same time cities like Machlipatnam, Surat and Seringapatam declined.
• The historic imperial city of Delhi became a dusty provincial town in the 19th century before it was rebuilt as the capital of British India.
• Delhi has been a capital for more than a 1,000 years, although with some gaps. As many as 14 capital cities were founded in a small area of about 60 square miles on the left-bank of the river Jamuna of these, the most important are the capital cities built between the 12th and 17th centuries.
• Shah Jahan built the most splendid capital of all. Shahjahanabad was begun in 1639 and consisted of a fort-palace complex and the city adjoining it. The Red Fort contained the palace complex.
• Delhi during Shah Jahan’s time was also a centre of Sufi culture. It had several dargahs, khanqahs and idgahs.
• Even this was no ideal city and its delights were enjoyed only by some. There were sharp differences between the rich-and the poor.
• In the first half of the 19th century the British lived along with the wealthier Indians in the Walled City. They learned to enjoy Urdu/Persian culture and poetry and participated in local festivals.
• But things did not remain the same after 1857. During the Revolt Delhi remained under rebel control for four months. When the British regained it they embarked on a campaign of revenge and plunder. They began to demolish everything that was associated with the Mughals. In fact, the British were very much annoyed with the Mughal emperor Bahadur Shah Zafar to see his active participation in the revolt.
• They either demolished mosques or put to other uses. For example, the Zinat-al-Masjid was converted into a bakery. No worship was allowed in the Jama Masjid for five years. One-third of the city was demolished and its canals were filled up.
• In the 1870s, the western walls of Shahjahanabad were broken to establish the railway and to allow the city to expand beyond walls.
• The British now began living in the sprawling Civil Lines area that came up in the north, away from the Indians in the Walled city.
• Delhi college was turned into a school, and shut down in 1877.
• Delhi emerged into the modern city only after 1911 when it became the capital of the British India.
• New Delhi was constructed as a 10-square-mile city on Raisina Hill, south of the existing city.
• Two architects, Edward Lutyens and Herbert Baker, were called on to design New Delhi and its buildings. It was kept in mind that the new buildings must assert British importance.
• New Delhi took nearly 20 years to build. The idea was to build a city that was a stark contrast to Shahjahanabad. There were to be no crowded mohallas, no mazes of narrow by-lanes. In New Delhi, there were to be broad, straight streets lined with sprawling mansions set in the middle of large compounds. The architects wanted New Delhi to represent a sense of law and order in contrast to the chaos of old Delhi.
• In 1947, India got independence but at the same time it was partitioned into India and Pakistan. This led to a large migration from Punjab that changed the social background of Delhi. An urban culture largely based on Urdu was overshadowed by new tastes and sensibilities, in food, dress and the arts.
• Inside the old city, the excellent system of water supply and drainage was neglected in the 19th century. The system of wells or baolis also broke down and channels to remove household waste were damaged.
• The population of Delhi was continuously growing at this time. The broken-down canals could not serve the needs of this ever-growing population.
• At the end of the 19th century a new system of open surface drains was introduced. But this system too was soon overburdened. The Delhi Municipal Committee was not willing to spend money on a good drainage system.
• At the same time, millions of rupees were being spent on drainage systems in the New Delhi area.
• The havelis or grand mansions in which the Mughal aristocracy lived in the 17th and 18th centuries also declined gradually. In fact the Mughal amirs were unable to maintain these large establishments under conditions of British rule. Havelis therefore began to be subdivided and sold.
• The colonial bungalow was quite different from the haveli. It was a large single-storeyed structure with a pitched roof and usually set in one or two acres of open ground.
• The Census of 1931 revealed that the Walled City area was crowded with as many as 90 persons per acre while New Delhi had only about 3 persons per acre.
• The poor conditions in the Walled City did not stop it from expanding. In 1888 an extension scheme called the Lahore Gate Improvement Scheme was planned by Robert Clarke for the Walled City residents. Streets strictly followed the grid system and were of identical width, size and character. Land was divided into regular areas for the construction of neighbourhoods. But even this scheme could not decongest the old city.
• The Delhi Improvement Trust was set up in 1936, and it built areas like Daryaganj South for wealthy Indians. Houses were grouped around parks. Within the houses, space was divided according to new rules of privacy.

Words that Matter:

• Presidency: The colonial India was divided into three Presidencies—Bombay, Madras and Calcutta for administrative purposes.
• Urbanisation: It is a process by which more and more people began to reside in towns and cities.
• Dargah: It refers to a tomb of a sufi saint.
• Khanqah: It refers to a sufi lodge often used as a rest house for travellers and a place where people came to discuss spiritual matters, got the blessings of saints and hear sufi music.
• Idgah: It refers to an open prayer place of Muslims primarily meant for id prayers.
• Cul-de-sac: Street with a dead end.
• Gul Farosan: A festival of flowers
• Renaissance: Literary rebirth of art and learning. It is a term often used to describe a time when there is great creative activity.
• Baolis: The system of wells
• Haveli: A grand mansion
• Amir: A nobleman during the Mughal period

Dateline:

• 1639 – Shahjahanabad was begun.
• 1792 – Delhi College was established.
• 1830-57 – A period of Delhi renaissance.
• 1877 – Viceroy Lytton organised a Durbar to acknowledge Queen Victoria as the Empress of India.
• 1888 – An extension scheme called the Lahore Gate Improvement Scheme was planned by Robert Clarke for the Walled City residents.
• 1911 – The capital of India was shifted from Calcutta to Delhi.
• 1936 – The Delhi Improvement Trust was set up.

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Resources – CBSE Notes for Class 8 Social

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Facts that Matter:

• Any substance, living being or service that has utility (i.e. can help us in any possible way) is said to be a resource.
• A resource has some value. The value can be associated with money (i.e. you have to pay money to get it), or just mental satisfaction (e.g. when you look at a beautiful painting or scenery, it feels pleasant, so the painting or scenery has utility).
• Examples of resources include books, stationery material, clothes, utensils, furniture, your teacher, school, rivers, water, electricity, and so on.
• The economic value of a resource may change with time.
• A substance may or may not be a resource depending on our knowledge. If we do not know how to write with a pen, then certainly the pen has no utility for us. So in this case the pen is not a resource. However, for those who know how to use a pen, it is a resource. So technology, ideas, knowledge, inventions, discoveries, etc. make a substance a resource.
• Time may also be a factor involved in making a substance a resource. Water has always been there, but its utility to manufacture electricity was not always known.
When people realised that water can be used to produce electricity, water became a resource in a new way.
• Resources may be natural, human, or human-made.
• Natural resources are those that are taken from nature. They are used without modifying them, i.e. in the same form as they exist in. Rivers, lakes, air, soils, minerals, trees, mountains, etc. are natural resources.
• On the basis of level of development of resource, a natural resource can be actual or potential. An actual resource is one which is used currently. We know their quantity. Examples are: coal deposits. A potential resource is one whose utility is not known at present or is not used despite having utility; instead it may be useful at some time in future. It means that it has the potential to have utility, although it does not have any today. Examples include uranium deposits in Ladakh.
• On the basis of origin, a resource can be abiotic or biotic. A biotic resource is one that has life. Examples: plants and animals. An abiotic resource is non-living. Examples: soils, rocks, furniture, books.
• Natural resources may also be classified as renewable and non-renewable. A renewable resource can be used without any risk of its ending up. They exist in unlimited quantity, for example solar energy, and wind energy. On the other hand, use of non-renewable resources need to be controlled since once they end up, they cannot be renewed. Examples: coal, petroleum.
• On the basis of distribution, a resource can be ubiquitous or localised. A ubiquitous^ resource is found everywhere, like air. A localised resource is, however, found in certain parts of the world only, like we cannot find coal everywhere.
• Human made resources have not been provided to us by nature. Human beings have used their intelligence to manufacture them for their own use. Examples include vehicles, buildings, roads, telephone, etc.
• Human resources include people who serve us in any way. Your teacher, doctor, carpenter, cobbler, etc. are human resources.
• Human resource development refers to the improvement of people’s skills so that they become more useful than before and are a better resource.
• Resource conservation is the concept of using resources carefully so that they do not end up quickly. The future generations also need the resources, but if we keep using them at a fast pace, they may end up, thus posing problems for the future. We should use resources in such a balanced way that we satisfy our needs as well as conserve them for future. This concept is called sustainable development.
• We can contribute to sustainable development by switching off lights when not needed, by recycling things and using them again, and in many more ways.

Flow Learning:

Words that Matter:

• Utility: A substance has utility if it can be used in any possible way to satisfy our needs.
• Value: Worth of a substance assessed on the basis of utility.
• Patent: It applies to the exclusive right over any idea or invention.
• Resource: Any substance having utility in any way is a resource.
• Technology: The application of the latest knowledge and skills in doing or making things is called technology.
• Natural Resource: Natural resources are those that are taken from nature.
• Actual Resource: An actual resource is one which is used currently and whose quantity is known.
• Potential Resource: A potential resource is one whose utility is not known at present or is not used despite having utility: instead it may be useful at some time in future.
• Abiotic Resource: An abiotic resource is a non-living resource.
• Biotic Resource: A biotic resource is a living resource.
• Renewable Resource: A renewable resource can be used without any risk of its ending up because they exist in unlimited quantity.
• Non-renewable Resource: A non-renewable resource is one which is present in limited quantity.
• Ubiquitous Resource: A ubiquitous resource is one that is found everywhere.
• Localised Resource: A resource that is found only in certain parts of the world and not everywhere.
• Human-made Resource:Resources invented by human beings by using their intelligence are called human made resources.
• Human Resources: A human being who can contribute to his family, society, or economy is called a. human resource.
• Human Resource Development: Human resource development refers to the improvement of people’s skills so that they become more useful than before and are a better resource.
• Stock of Resource: The amount of resource, available for use is called its stock.
• Resource Conservation: Resource conservation is the concept of using resources carefully so that they do not end up quickly.
• Sustainable Development: It is the concept of using resources in a balanced way so that our purpose is solved, as well as they are also conserved for the future.

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Land, Soil, Water, Natural Vegetation and Wildlife Resources – CBSE Notes for Class 8 Social

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Facts that Matter:

• The quality of land, soil, water, natural vegetation, animals, and the usage of technology are important factors in controlling the standard and way of life people lead at a particular place.
• Land covers just about 30% of the surface of the earth. It is not suitable for living everywhere, because of a lot of additional conditions that affect life. Parts of land not suitable for living are said to be inhabitable while the ones where people live are said to be habitable.
• Some factors affecting the habitability of a place are topography, height from sea level, climate, fertility of soil, vegetation, etc. People cannot live in dense forests or in deserts. They cannot live on high slopes in mountainous areas, or in low-lying areas where there is possibility of floods and water logging. Plains and river valleys are the places where agriculture is suited, so most of the world population lives in such areas, and these areas are heavily populated.
• The purpose and way in which land is used is called land use. Land use may be for agriculture, forestry, mining, building houses, roads, setting up of industries, or various other purposes.
• Factors determining the land use include physical factors like topography, availability of water, climate, minerals  soil, etc, or human factors like demography (population pattern), technology and education.
• Land usually has ownership. It may be private land or community land. Private land is owned by an individual or group of individuals, like a house is private land. Community land is meant for use by anyone in the society, like land for collection of fodder, fruits, etc. Community lands are also called common property resources.
• Since population is always growing at a fast pace, the demand for land is increasing, whereas the availability of land is limited.
• Land degradation, landslides, soil erosion, desertification are major threats to the environment.
• Due to the huge demand for land, people have also started reducing forest cover in order to make them habitable. This has resulted into deforestation. Afforestation (growing trees), regulated use of chemical pesticide and checking overgrazing by animals are some general methods to conserve these valuable natural resources.
• The word soil refers to the thin layer of grainy substance covering the surface of the earth. This layer is made of organic matter, minerals and weathered rocks. The long process of weathering is responsible for the formation of soil.
• Weathering refers to the breaking up and decay of exposed rocks. This breaking up and decay is caused by temperature fluctuations, frost action, plants, animals and even human activity. Due to weathering, in thousands of years, soil is formed.
• The nature of the parent rock and climatic factors are major factors of soil formation. Other factors include topography, role of organic material and time taken for the composition of soil formation.
• Soil erosion and depletion pose major threats to the quality and resourcefulness of soil. Degradation takes place by both human and natural factors. Deforestation,
overgrazing, overuse of chemical fertilisers or pesticides, rain wash, landslides and floods lead to degradation of soil.
• Mulching is the process of covering the bare ground between plants with a layer of organic matter like straw. This helps in retaining soil moisture.
• Farmers use stones, grass and soil to build barriers along contours. Trenches are made in front of them to collect water.
• Terrace farming is the method of farming in which broad flat steps or terraces are made on the steejp slopes so that flat surfaces are available to grow crops. This helps in controlling soil erosion.
• In intercropping, different crops are grown in alternate rows and are sown at different times to protect the soil from being washed away by rain.
• Ploughing parallel to the contours of a hill slope to form a natural barrier for water to flow down a slope is called contour ploughing.
• Rows of trees are planted in certain areas to check wind movement. Such rows are called shelter belts. These trees are supposed to bind the soil, thus preventing them from being eroded away easily.
• Water covers about 75% of the surface of the earth. Therefore, the earth is called the water planet. Ocean water is saline and not fit for human consumption. Fresh water is just about 2.7% of tile total water. So fresh water is very scarce.
• We use water for a lot of purposes. Life is impossible without water.
• Water shortage is a common problem in many parts of the world. It may be a consequence of variation in rain patterns or contamination of water sources.
• Steps need to be taken to conserve water. Water is renewable, but its overuse and pollution make it unfit for use. Sewage, industrial waste, chemicals, etc pollute water with nitrates, metals and pesticides.
• Natural vegetation and wildlife exist in the biosphere. The supporting and interdependent life-system that exists in the biosphere is called ecosystem.
• Plants provide us with a number of important products, shelter to animals, liberate oxygen which supports life, protects soil and give us much of our food.
•. Animals, birds and insects (wildlife) are also helpful in a lot of ways. Insects like bees provide us honey and a bird like the vulture cleanses the environment by feeding on dead livestock.
• Vegetation depends on temperature and moisture of a region. Forests, grasslands, scrubs and tundra are major vegetation types across the world.
• Heavy rainfall supports huge trees. Low moisture means less dense forests and smaller trees. In deserts, we have thorny shrubs and scrubs.
• Forests are classified as evergreen and deciduous. The first type never shed their leaves, but the second type shed their leaves at a particular time of the year. Both these types are further classified into temperate and tropical based on their location.
• There are huge concerns about conservation of these important resources. We must contribute to this. Natural parks, wildlife sanctuaries and biosphere reserves are ways to protect vegetation and wildlife.
• Conservation of plants and animals is a moral duty of every human being.

Flow Learning:

Words that Matter:

• Land: The surface of the earth which is solid and covers about 30% of the total surface of the earth is called land.
• Land Use: The way in which a particular section of land is being used is called land use. .
• Private Land: A part of land owned by a particular individual or group of individuals is called private land.
• Community Land: A part of land not owned by anyone but meant for use by a large group of people living in a society, is called community land.
• Deforestation: The action of cutting down trees is called deforestation.
• Afforestation: The action of planting trees is called afforestation.
• Soil: The thin layer of grainy substance covering the surface of the earth is called soil.
• Weathering: Weathering refers to the breaking up and decay of exposed rocks. This breaking up and decay is caused by temperature fluctuations, frost action, plants, animals and even human activity.
• Parent Rock: The original rock from which soil has been formed is called its parent rock.
• Mulching: Mulching is the process of covering the bare ground between plants with a layer of organic matter like straw.
• Terrace Farming: Terrace farming is the method of farming in which broad flat steps or terraces are made on the steep slopes so that flat surfaces are available to grow crops.
• Intercropping: In intercropping, different crops are grown in alternate rows and are sown at different times to protect the soil from being washed away by rain.
• Contour Ploughing: Ploughing parallel to the contours of a hill slope to form a natural barrier for water to flow down a slope is called contour ploughing.
• Shelter Belts: Rows of trees that are planted in certain areas to check wind movement are called shelter belts.
• Fresh Water: Water fit for human consumption is called fresh water.
• Water Cycle: The natural process of the constant motion of water through evaporation, condensation and rainfall is called water cycle.
• Rain Water Harvesting: The process of conserving water in which rainwater is collected so that it can come of use in times of water scarcity is called rain water harvesting.
• Biosphere: The narrow zone of contact between the lithosphere, hydrosphere and atmosphere is called the biosphere.
• Ecosystem: The supporting and interdependent life-system that exists in the biosphere is called ecosystem.
• Natural Vegetation: Plants and trees constitute natural vegetation.
• Wildlife: The animal kingdom, which consists of animals, birds, aquatic creatures and insects, is called wildlife.
• Scavenger: A bird or animal which feeds on dead livestock is called a scavenger.
• Tundra: The type of vegetation found in very cold regions like the Arctic is called Tundra vegetation.
• Evergreen Forests: The forests which never shed their leaves are called evergreen forests.
• Deciduous Forests: The forests which shed their leaves once at a particular time o.f the year are called deciduous forests.
• Vanamahotsava: The social programme of planting trees, organised at community level is called vanamahotsava.
• National Parks: A national park is a natural area supposed to be used to protect the ecological integrity of one or more ecosystems for the present and future generations.
• Wildlife Sanctuaries: A wildlife sanctuary is similar to a national park, but it is supposed to protect a particular animal, in some cases, or wildlife in general, in other cases.
• Biosphere Reserves: These are series of protected areas linked through a global network, intended to demonstrate the relationship between conservation and development.

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Mineral and Power Resources – CBSE Notes for Class 8 Social

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Facts that Matter:

• A naturally occurring substance having a definite chemical composition is called a mineral. Minerals are found in certain areas only and not everywhere.
• Minerals are formed in different conditions and human activities do not play any role in their formation. Instead only natural processes are involved.
• Minerals can be identified on the basis of their physical properties like colour, density, hardness and chemipal properties like solubility.
• On the basis of composition, we classify minerals as metallic and non-metaliic.
• Metallic minerals contain metal. The metal is present in raw form, that is, it contains impurities and it needs to be processed in order to yield the pure metal.
• Ferrous minerals and non-ferrous minerals are a classification of metallic minerals. Ferrous minerals contain iron. Examples are iron ore, manganese ore and chromites. Non-ferrous minerals do not contain iron as a constituent. Examples include gold, silver, copper, lead.
• Non-metallic minerals do not contain metals. Instead they contain impure compounds or mineral fuels. Examples: limestone, mica, coal and petroleum.
• Extraction is the process of taking out minerals from under the earth’s surface so that useful materials can be derived from them.
• Mining is a process of extraction or taking out minerals from rocks under the earth’s surface.
• In open-cast mining, minerals lying at shallow depths are taken out by removing the surface layer. In shaft mining, deep bores (called shafts) are made to reach mineral deposits lying at large depths.
• Drilling is another method of extraction in which deep wells are bored to take out minerals.
• Quarrying refers to the process of extraction in which minerals lying very close to the surface are extracted just by digging them out.
• Metallic minerals are generally found in igneous rocks and metamorphic rocks in plateaus. Non-metallic minerals are usually found in sedimentary rock formation in plains and young-fold mountains.
• Major regions having large iron deposits are China and India in Asia; Russia, Ukraine, Sweden and France in Europe; the Canadian Shield region in North America; and Brazil in South America. Brazil is the largest producer of high grade iron ore.
• Asia produces over half the total tin production in the world. China leads in the production of lead, antimony, tin and tungsten.
• North America is divided into three zones to describe the presence of mineral deposits. These are Canadian region north of the Great Lakes, the Appalachian region and the mountain ranges in the western part of the continent.
• Chile and Peru in South America are leading producers of copper. Brazil and Bolivia are important producers of tin.
• Africa is the continent richest in mineral resources. South America, Zimbabwe and Zaire are the world’s most important producers of gold.
• Australia produces the largest quantity of bauxite. It also produces gold, diamond, iron, tin and nickel. The areas called Kalgoorlie and Coolgardie have large deposits of gold.
• In India, high grade iron ore is produced in Jharkhand, Odisha, Chhattisgarh, Madhya Pradesh, Goa, Maharashtra and Karnataka. Bauxite is produced in Jharkhand, Orisha, Chhattisgarh, Madhya Pradesh, Gujarat, Maharashtra and Tamil Nadu. Mica deposits are found in Jharkhand, Bihar, Andhra Pradesh and Rajasthan. India is the largest producer and exporter of mica in the world.
• Kolar in Karnataka has large deposits of gold. India is a leading producer and exporter of salt.
• Minerals are used for a lot of purposes. Copper is a metal used in nearly everything. Silicon is obtained from quartz. It is a basic tool of the computer industry.
• Minerals are non-renewable since their formation is a long process. Recycling of metals and reducing wastage are ways to conserve them.
• Power means energy. We require power for everything.
• Power resources are of two types: conventional and non-conventional.
• Conventional power sources are those that have been in use for a long time. Fossil fuels and firewood are Examples.
• Non-conventional power sources are those power sources that have come into use recently due to the depleting conventional resources and growing awareness.
• Firewood is widely used in India for cooking and heating. Fossil fuels are what the remains of plants and animals converted into after they remained buried under the earth for millions of years.
• Coal, petroleum and natural gas are important fossil fuels. Electricity from coal is called thermal power. Petroleum and its derivatives are called black gold because of their importance. Natural gas is found with petroleum deposits.
• Hydel power is the energy possessed by river water (stored in dams) or rain water falling from great heights. One-fourth of the world’s electricity is produced from hydel power.
• Solar energy, wind energy, geothermal energy, nuclear power and tidal energy
are examples of non-conventional power sources.
• Solar energy is the heat and light energy captured from the sun. Solar cells help to convert this energy to electricity. Solar energy is used in solar heaters, solar cookers, solar dryers, etc.
• Wind energy is the energy possessed by moving air (wind). Windmills are used to^\ convert wind energy to electricity. Wind farms having clusters of windmills are located in coastal regions and mountain passes.
• Nuclear power is energy possessed by the nuclei of atoms of naturally occurring radioactive elements like uranium, thorium, etc.
• Geothermal energy is the heat energy obtained from the inside of the earth. The temperature inside the earth increases as we go deeper. This heat is used to produce electricity. It is accessed in the form of hot springs.
• Tidal energy is the energy generated from tides. It is harnessed by building dams at narrow openings of the sea.
• Biogas is a gaseous fuel obtained from the decomposition of organic waste like dead plant and animal material or animal dung and kitchen waste. It is an excellent fuel for cooking and lighting, and is environment-friendly.

Flow Learning:

Words that Matter:

• Mineral: A naturally occurring substance having a definite chemical composition is called a mineral.
• Rock: A rock is an aggregate of one or more minerals, without definite composition of constituent of minerals.
• Ore: An ore is a rock from which minerals are mined.
• Metallic Minerals: Metallic minerals are those containing metal. The metal is present in raw form, that is, it contains impurities and it needs to be processed in order to yield the pure metal.
• Ferrous Minerals: Ferrous minerals are the ones containing iron as a constituent.
• Non-ferrous Minerals: Non-ferrous minerals are the ones that do not contain iron as a constituent.
• Non-metallic Minerals: Non-metallic minerals are the ones that do not contain metals.
Instead they contain impure compounds or mineral fuels.
• Extraction: Extraction is the process of taking out minerals from under the earth’s surface so that useful materials can be derived from them.
• Mining: Mining is a process of extraction or taking out minerals from rocks under the earth’s surface.
• Open-cast Mining: Open-cast mining is a method of extraction in which minerals lying at shallow depths are taken out by removing the surface layer.
• Shaft Mining: Shaft mining is a method of extraction in which deep bores (called shafts) are made to reach mineral deposits lying at large depths.
• Drilling: Drilling is another method of extraction in which deep wells are bored to take out minerals.
• Quarrying: Quarrying refers to the process of extraction in which minerals lying very close to the surface are extracted just by digging them out.
• Conventional Sources of Energy: Conventional power sources are those that have been in use for a long time.
• Non-conventional Power Sources: Non-conventional power sources are those power sources that have come into use recently due to the depleting conventional resources and growing awareness.
• Fossil Fuels: Fossil fuels are what the remains of plants and animals converted into after they remained buried under the earth for millions of years.
• Thermal Power: The electricity obtained from coal is called thermal power.
• Coal: Coal is a fossil fuel that was formed millions of years ago when giant ferns and swamps got buried under the layers of the earth.
• Petroleum: Petroleum is a thick black liquid fossil fuel found between layers of rocks
and drilled from oil fields.
• Hydel Power: Hydel power is the energy possessed by river water (stored in dams) or rain water falling from great heights.
• Solar Energy: Solar energy is the heat and light energy captured from the sun.
• Solar Cell: Solar cells are devices to convert solar energy into electricity.
• Wind Energy: Wind energy is the energy possessed by moving air (wind).
• Nuclear Power: Nuclear power is energy possessed by the nuclei of atoms of naturally occurring radioactive elements like uranium, thorium, etc.
• Geothermal Energy: Geothermal energy is the heat energy obtained from the inside of the earth.
• Tidal Energy: Tidal energy is the energy generated from tides.
• Biogas: Biogas is a gaseous fuel obtained from the decomposition of organic waste like dead plant and animal material or animal dung and kitchen waste.

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Agriculture – CBSE Notes for Class 8 Social

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Facts that Matter:

• We divide economic activities into three categories: primary, secondary and tertiary. Agriculture, an activity that is related directly to the extraction and production of natural resources, is a primary activity. Manufacturing of steel and baking of bread are secondary activities since they are not directly related to the extraction or production of natural resources, but their utilisation. Transport and trade are tertiary activities since they do not come in either category.
• Two-thirds of India’s population depends on agriculture.
• Some of the important inputs required in agriculture are seeds, fertilisers, machinery and labour. Operations involved are ploughing, sowing, irrigation, weeding and harvesting. Outputs include cops, wool, dairy and poultry products.
• Two main types of farming practised are subsistence farming and commercial farming.
• Subsistence farming is practised solely to meet the needs of the farmer’s family. Therefore, the practices involved are usually old-fashioned. Use of modern technology is minimum and most work is done by household labour.
• In Intensive subsistence agriculture, simple tools and huge labour are used by a farmer to cultivate a small plot of land. More than one crop is grown annually in favourable conditions. Rioe is the major crop. This form of agriculture is seen in the thickly populated areas of the monsoon regions of south, south-east and east Asia.
• Shifting cultivation is a class of primitive subsistence agriculture. In this, a plot of land is cleared by felling the trees and burning them. The ashes are then mixed with soil and crops are grown. After some time, the land is abandoned and the farmers move to a different place. This type of farming is common in the thickly forested areas of the Amazon basin, tropical Africa, parts of South-east Asia and north-east India. It’ is also called “slash and burn” agriculture.
• Nomadic herding refers to the practice in which herdsmen move from place to place with their animals for fodder and water. Animals usually reared are the yak, sheep, camel and goats.
• Commercial farming is the practice in which crops are grown exclusively for commercial purpose, i.e. for sale in the market. A large area is cultivated and huge capital is involved unlike subsistence farming. Machines are used to a large extent.
• Commercial grain farming is a class of commercial farming. Crops like wheat and maize are grown for commercial purpose. The temperate grasslands of North America, Europe and Asia are some common areas where it is seen.
• Mixed farming is another type of commercial farming. The land is used for growing food and fodder crops and rearing livestock. Some areas where it is followed are Europe, eastern USA, Argentina, south-east Australia, New Zealand and South Africa.
• Plantations are a type of commercial farming where only a single crop (like tea, coffee, sugarcane, cashew, rubber, banana or cotton) is grown. Large amount of labour and capital are required. The produce is processed in the farm itself or nearby factories.
• Rice is the major food crop of the world. It is the staple diet in tropical and sub-tropical parts. Its cultivation needs high temperature, humidity and rainfall. China and India are the largest producers of rice in the world.
• Wheat thrives best in well-drained loamy soil. In addition, it needs moderate temperature and rainfall during growing season and bright sunshine at harvesting. USA is a major producer.
• Millets are coarse grains. Jowar, bajra and ragi are major millets grown in India.
• Maize requires moderate temperature, rainfall, good sunshine and well-drained fertile soils.
• Cotton grows best on black and alluvial soils. It needs high temperature, light rainfall, 210 frost free days and bright sunshine.
• Jute (called the Golden Fibre) is grown in tropical areas. India and Bangladesh are leading producers.
• Coffee grows well on hill slopes. Brazil is the leading producer.
• Tea is a beverage crop grow on plantations. It needs well-drained loamy soils ad gentle slopes. Large labour is required.
• Agricultural development refers to the effort to increase farm production so as to meet growing demand of increasing population. Mechanisation, a part of agricultural development, means using more machines than human labour.
• A typical Indian farm is about 1.5 hectares in area, whereas a typical USA farm is about 250 hectares.
• In the USA, farmers use very modern methods for agriculture. In India, however, obsolete methods are used in most parts. Mechanisation is not seen much in India as compared to USA.
• A farmer in India generally works as a “peasant” whereas in the USA, he works as a complete businessman.

Flow Learning:

Words that Matter :

• Primary Activities: Activities which involve direct extraction and production of natural resources are called primary activities: For example agricultural farming, sericulture, pesciculture, etc.
• Secondary Activities: Activities which are concerned with the processing of natural resources are called secondary activities.
• Tertiary Activities: Activities which fall neither in the primary category nor the secondary category are called tertiary activities. They do not use natural resources directly.
• Agriculture: Agriculture is the primary activity that involves cultivation of crops, fruits, vegetables, flowers and rearing of livestock.
• Subsistence Farming: Subsistence farming is the form of agriculture practised solely to meet the needs of the farmer’s family: The practices involved are usually old- fashioned.
• Intensive Subsistence Agriculture: In intensive, subsistence agriculture, simple tools and huge labour are used by a farmer to cultivate a small plot of land.
• Shifting Cultivation: Shifting cultivation is the form of agriculture in which a plot of land is cleared by felling the trees and burning them. The ashes are then mixed with soil and crops are grown. After some time, the land is abandoned and the farmers move to a different place.
• Nomadic Herding: Nomadic herding refers to the practice in which herdsmen move from place to place with their animals for fodder and water.
• Commercial Farming: Commercial farming is the practice in which crops are grown exclusively for commercial purpose, i.e. for sale in the market.
• Commercial Grain Farming: It is a class of commercial farming in which crops like wheat and maize are grown for commercial purpose.
• Mixed Farming: It is a type of commercial farming in which land is used for growing food and fodder crops and rearing livestock.
• Plantations: These are a type of commercial farming where only a single crop (like tea, coffee, sugarcane, cashew, rubber, banana or cotton) is grown.
• Food Crops: Crops like rice, wheat, maize, millets are called food crops.
• Fibre Crops: Crops like jute and cotton are called fibre crops. Their usage is not as food.
• Beverage Crops: Tea and coffee are called beverage crops.
• Agricultural Development: Agricultural development refers to the effort to increase farm production so as to meet growing demand of increasing population.
• Mechanisation: This refers to the process of using machines more than human labour.

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 Industries – CBSE Notes for Class 8 Social

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Facts that Matter:

• Secondary activities are those that involve processing of natural resources. Manufacturing is a secondary activity. Manufacturing refers to changing raw materials to a product, i.e. to a usable form, which can be more valuable to people.
• Industry refers to an economic activity that is concerned with production of goods, extraction of minerals or provision of services.
• We classify industries on the basis of raw materials, size and ownership.
• On basis of raw materials, industries are agro-based, mineral-based, marine-based or forest-based.
• The raw material of agro-based industries consists of plant and animal based products. Some examples are food processing, cotton textile industry and leather industry.
• The raw material used in mineral-based industries consists of mineral ores. The products of mineral-based industries are used in other industries as well. We can understand it better with an example: heavy machinery made of iron, which is used in most industries, actually comes after processing of iron ore in a mineral-based industry.
• Marine-based industries use products obtained from the sea and oceans as raw materials. Sea food industry is one such industry.
• A forest-based industry uses forest produce as raw material. Examples are paper industry and furniture.
• Based on size, industries can be classified into small-scale and large-scale industries. Cottage or household industries are .examples of small-scale industries. The products here are manufactured by hands, with less use of capital and technology. Investment of capital and use of technology is huge in large-scale industries.
• On the basis of ownership, industries are classified into private sector, state owned (public sector), joint sector and cooperative sector. Private sector industries are owned by individuals or a group of individuals. Public sector industries are owned by the government. Joint sector industries are owned and operated by the state and individuals. Maruti Udyog is an example of such an industry. Cooperative sector industries are owned and operated by the producers or suppliers of raw materials, workers or both. AMUL is one such industry.
• The location of industries is affected by the availability of raw material, land, water, labour, power, capital, transport and market.
• An industrial system, like farming process, consists of inputs, processes and outputs. Raw materials, labour and cost of land, transport, power and other infrastructure constitute the inputs. Processes include all activities involved in converting the raw material to finished products. The finish products along with the income earned by its trade are outputs. .
• Major industrial regions of the world are eastern North America, western and central Europe, eastern Europe and eastern Asia. Such areas are usually located in temperate areas, near sea ports and coal fields.
• The iron and steel industry is a mineral-based industry whose products are used as raw material for other industries.
• Inputs in iron and steel industry: iron ore, coal, limestone, human labour, capital, and infrastructure. Processes involved: smelting, refining. Outputs obtained: steel.
• Steel is called the backbone of modern industry. Most common objects are made of steel. In India most important steel producing centres are spread over the states of West Bengal, Jharkhand, Orissa and Chhattisgarh.
• Tata Iron and Steel Company Limited (TISCO) was the only one iron and steel plant in India till independence. It is located in Jamshedpur. Several iron and steel industries were set up after independence. This led to rapid industrial development in India.
• Pittsburgh is an important steel city of USA.
• The cotton textile industry is one of the oldest industries in the world. India is renowned for producing excellent quality cotton. The first mechanised textile mill in India was established in Mumbai in 1854. Rapid expansion of the industry took place owing to the warm, moist climate, the presence of a port nearby, and availability of raw material and labour at cheap cost.
• Ahmedabad is the second largest textile city in India after Mumbai. It is referred to as the “Manchester of India”. In recent years textile mills here have started getting closed down due to several problems.
• Osaka is the “Manchester of Japan”.
• The Information Technology (IT) sector deals in the storage, processing and distribution of information. The major hubs of IT industry are Silicon Valley in USA and Bangalore in India.

Flow Learning:

Words that Matter:

• Manufacturing: Manufacturing refers to changing raw materials to a usable form, which can be more valuable to people.
• Product: A product is something obtained from raw materials by certain processes, so that it is something usable and of importance.
• Industry: Industry refers to an economic activity that is concerned with production of goods, extraction of minerals or provision of services.
• Agro-based Industries: These are industries that use plant and animal based products as raw material.
• Mineral-based Industries: These are industries that use mineral ores as their raw material.
• Marine-based Industries: These are industries that use sea and ocean products as their raw material.
• Forest-based Industries: These are industries that use forest produce as raw material.
• Small-Scale Industries: These are industries that run on little capital and infrastructure.
• Large-Scale industries: These are industries that run on large amount of capital and have a big infrastructure.
• Private-Sector Industries: These are industries owned and run by an individual or group of individuals.
• Public-Sector Industries: These are industries owned and run by the government.
• Joint-Sector Industries: These are industries owned and run by the state as well as individuals.
• Cooperative Sector Industries: These are industries owned and operated by producers or suppliers of raw materials.
• Smelting: Smelting is the process of extracting the minerals from their ores by heating beyond their melting point.
• Refining: Refining is the process of yielding the highest possible purity of metal obtained from mineral.
• Steel: Steel is an alloy of iron obtained from the iron ore.
• Information Technology Industry: The IT industry deals in the storage, processing and distribution of information.

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 Human Resource – CBSE Notes for Class 8 Social

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Facts that Matter:

Human beings are the most important resource of a nation. They are significant because had they not utilised their brains, the other resources of nature would not have found any utility. In other words, human resource is the ultimate resource.
The way in which people are spread across the earth’s surface is known as the pattern of population distribution. Some areas are very crowded (high density) while some are less crowded (low density). Population density depends on the climate conditions and topography of the place, like few people live in high latitude areas, tropical deserts, mountainous terrains, and forest areas, whereas a large number of people reside in plains.
Density of population is defined as the average number of people living in a unit area of the earth’s surface. The density of a particular region is calculated by dividing the population of the region by its area.
Topography, favourable climate, fertility of soils, availability of fresh water, minerals are major geographical factors affecting population density of a region. People prefer to live on plains more than mountains or plateaus and they live more in moderate climates than extreme hot or cold. From the agriculture point of view, fertile lands are preferred. Areas with mineral deposits are more populated.
Some social factors that boost the density of population in a region are better housing, education and health facilities.
Places with cultural or historical significance are usually populated.
Employment opportunities are another attraction for large chunks of population.
The term population change refers to change in the population with respect to time. The population of the world is never stable; the number of births and deaths affect its change.
With better health facilities due to development in medical science, now the number of deaths is lower than before.
Birth rate is a statistic that measures the number of live births per 1000 people. Death rate is a statistic that measures the number of deaths per 1000 people.
When we talk of the population of a particular region, country or continent, and not the whole world, then along with birth and death rate, another factor affecting population change is migration. Migration refers to the movement of people from one area to another.
Since births and deaths are natural causes of population change, the difference between the birth and death rate is called natural death rate.
People leaving a country are called emigrants and the phenomenon is called emigration. People arriving in a country’are called immigrants and the phenomenon is called immigration. People usually migrate from less developed areas to more developed ones, in search for better employment opportunities, among other facilities.
The pattern of population change is different for different parts of the world.
The structure of the population with various respects Age like age, sex, literacy, occupations, health facilities, 75+ economic condition, etc is called population composition.
A population pyramid is a pictorial way to describe 55-59 the population composition. An age-sex pyramid of India is shown in the figure.

The shape of population pyramid of a country is indicative of a lot of information about the country.
The size towards the bottom may be used to 20-24 estimate the birth rate, while the size towards the top to estimate the death rate.
The youngsters (ages 0-15) and senior citizens (aged 65 above) are said to fall under the “dependent” group.
They are considered to be economically inactive; they depend on the working class for their living. The middle age group constitutes the working class.
A population pyramid in which the base is broad and the top part is narrow means that although a large amount of births take place, not all grow up to be adults and old; it means many die before reaching these ages. This indicates a large death rate and Kenya shows such a pyramid. This means a high population growth rate.
In countries like India, the death rate is decreasing, so the pyramid is broad in the younger age groups, and the size of the pyramid decreases steadily.

Floe learning:

Words that Matter :

• Human Resources: Human beings who are healthy, educated, and mentally strong can prove to be useful for a country or community and are treated as resources themselves, called human resources.
• Population: The total number of people living in a particular region is said to be the population of that particular region.
• Pattern of Population Distribution: The way in which people are spread across the earth’s surface is known as the pattern of population distribution.
• Population Density: The average number of people living in a unit area of a particular region, calculated by dividing the total population of the region by the total area of that region, is called the population density of that region.
• Population Change: The change in the population, when described over a certain length of time, is called population change.
• Birth Rate: Birth rate is a statistic that measures the number of live births per 1000 people.
• Death Rate: Death rate is a statistic that measures the number of deaths per 1000 people.
• Life Expectancy: Life expectancy is the number of years that an average person can expect to live, calculated according to existing data for the particular region.
• Migration: Migration refers to the movement of people from one area to another.
• Natural Death Rate: The difference between the birth and death rate is called natural death rate.
• Emigrants/Emigration: People leaving a country are called emigrants and the phenomenon is called emigration.
• Immigrants/Immigration: People arriving in a country are called immigrants and the phenomenon is called immigration.
• Population Composition: The structure of the population with various respects like age, sex, literacy, occupations, health facilities, economic condition, etc is called population composition.
• Population Pyramid: A population pyramid is a pictorial way to describe the population composition.

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The Indian Constitution – CBSE Notes for Class 8 Social

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Facts that Matter:

• A society is bound to certain set of rules which makes it what it is and differentiates it from other kinds of society. These rules, in large societies in which different communities of people live together, are formulated through consensus. In modern countries this consensus is usually available in written form. A written document in which we find such rules is known as a Constitution.
• Constitution lays certain ideals that form the basis of the kind of country that we as citizens aspire to live in.
• A Constitution helps serve as a set of rules and principles that all persons in a country can agree upon as the basis of the way in which they want the country to be governed. This includes the type of government and also an agreement on certain ideals that they all believe the country should uphold.
• Principles and ideals of a monarchy are quite different from those of a democracy. Therefore soon after the transition in the governing system in Nepal the government started the process of making a new Constitution of Nepal because the earlier one did not suit their new setup.
• The country of Nepal needs to change all its constitutive rules in order to usher in a new democratic society for which people had struggled for a long period.
• The Constitution defines the nature of a country’s political system. In a monarchy king is the supreme power whereas in a democracy people rule the country. The government is run by the representatives elected by people at large.
• The Constitution also describes rules that guard against misuse of power by the leaders. In India such provisions have been made in the section of Fundamental Rights.
• The Indian Constitution guarantees the Right to Equality. In one of the Fundamental Rights to all persons and says that no citizen can be discriminated against on grounds of religion, race, caste, gender, and place of birth.
• The Constitution ensures that a dominant group does not use its power against other, less powerful people or groups.
• The Constitution also contains rules that ensure that minorities are not excluded from anything that is normally available to the majority. Thus the Constitution prevents the tyranny or domination by the majority of a minority.
• The Constitution helps to protect us against certain decisions that we might take that could have an adverse effect on the larger principles that the country believes in.
• After independence it was unanimously agreed that India should be a democratic state where everyone must avail equal opportunity.
• For this there was a need for Constitution which could ensure a perfect democracy. A group of around three hundred people who became members of the Constituent Assembly in 1949 and who met periodically for the next three years to write Indian Constitution.
• There were so many factors, most of them quite contrary to each of them, to be assimilated with clear cut explanations that made the task very difficult. However, the Constitution was finalised with a lot of unique features.
• Federalism is the prime feature of our Constitution which refers to the existence of more than one level of government in the country. In India there are governments at the state and the centre. Panchayati Raj is the third tier of the government.
• While each state in India enjoys autonomy in exercising powers on certain issues, they are bound to follow the laws of the central government as a matter of national concern. The Constitution clearly defines the jurisdictions of powers of the government at state and that at centre.
• Parliamentary form of Government is the other feature of Indian Constitution which provides that the different tiers of governments shall constitute of the representatives elected by the people. It also guarantees universal adult suffrage for all citizens.
• The provision for separation of powers in the Constitution of India recommends for three organs of the State: the legislature, the executive and the judiciary. The legislature refers to our elected representatives whereas the executive refers to a smaller group of people who are responsible for implementing laws and running the government and the judiciary refers td the system of courts in the country for preventing the misuse of power by any branch of the State. It also ensures the balance of power between all three organs.
• The feature of Fundamental Rights is the ‘conscience’ of the Indian Constitution. These Rights protect citizens against the arbitrary and absolute exercise of power by the State. The Constitution, thus, guarantees the rights of individuals against the State as well as against other individuals.
• The Fundamental Rights in the Indian Constitution include:
1. Right to Equality,
2. Right to Freedom,
3. Right against Exploitation,
4. Right to Freedom of Religion,
5. Cultural and Educational Rights,
6. Right to Constitutional Remedies.
• In addition to the Fundamental Rights there is the provision of Directive Principles of State Policy which ensure greater social and economic reform, and serve as a guide to the independent Indian State to institute laws and policies that help reduce the poverty of the masses.
• Secularism, a key feature of Indian Constitution, defines that a secular state is one in which the state does not officially promote any one religion as the state religion.
• The Constitution, thus, plays a crucial role in laying out the ideals that we would like all citizens of the
country to adhere to, including the representatives that we elect to rule us.

Words that Matter :

• Constitution: Usually a written document which contains the rules of governing a sovereign state.
• Consensus: Agreement of all the people on an issue.
• Democracy: A form of government in which people at large hold the ultimate power of governance. The representatives of people constitute the government and undertake the Constitutional responsibilities in order to achieve the ideals of Constitution.
• Fundamental Rights: The set of Rights which ensures the life of dignity and honour to all who live in its jurisdiction.
• Equality: State of being equal in all respects.
• Majority: Maximum in number.
• Minority: Minimum in number.
• Federalism: The existence of more than one levels of government in the country.
• Representative: The person who is elected by people through a general election to represent a constituency in the government.
• Secularism: A system under which a state does not officially promote any one religion as a state religion.

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Understanding Secularism – CBSE Notes for Class 8 Social

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Facts that Matter:

• The term secularism refers to the separation between the power of religion and the power of the State. This is important for a country to function democratically.
• There are two chief reasons why the separation between religion and State is important.
– The first is to prevent the domination of one religion over another.
– The second is to protect the freedom of individuals to come out of their religion, embrace another religion or have the freedom to interpret religious teachings differently. We can give example of the practice of untouchability which allowed upper caste people to dominate lower caste people.
• Secularism’s opposition to institutionalised religion means that it promotes freedom and equality between and within religions.
• Indian secularism does protect individual’s religious freedom by maintaining a separation from religion.
• The Indian State is not ruled by a religious group. It also does not support any one religion.
• In India, government spaces such as law courts, police stations, government schools and offices are not supposed to demonstrate or promote any one religion.
• Indian secularism follows a strategy of non-interference. But at the some time it also intervenes in religion. Again we can give example of the practice of untouchability. The Indian Constitution bans this practice. In this instance the State is intervening in religion in order to end a social practice that it believes discriminates and excludes and that violates the fundamental rights of lower caste people.
• The intervention of the State can also be inform of support.
• Indian secularism is different from that of other democratic countries such as the United States of America. There is a strict separation between religion and the State in American secularism but in Indian secularism, as mentioned above, the State can intervene in religious affairs.
• In Indian secularism, though the State is not strictly separate from religion it does maintain a principled distance vis-a-vis religion. This means that any interference in religion by the State has to be based on the ideals laid out in the Indian Constitution.

Words that Matter:

• Secularism: It refers to the separation of religion from the State.
• Coercion: Forcing someone to do something. In the chapter, the term refers to the force used by a legal authority such as the State.
• Freedom to interpret: It refers to the freedom that all persons shall have to understand things in their own way. In the chapter, it refers to an individual liberty to develop their own understanding and meaning of the religion they practice.
• Intervene: In the chapter, the term refers to the State’s efforts to influence a particular matter in accordance with the principles of the Constitution.

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Why Do We Need a Parliament? – CBSE Notes for Class 8 Social

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Facts that Matter:

• India got freedom after a long and tough struggle. In this struggle for freedom people from different backgrounds participated. They were greatly inspired by the ideas of freedom, equality and participation in decision-making.
• The British government had created such a havoc that they never dared to criticise any of their decisions even if they did not agree with them.
• The freedom movement changed this situation. The nationalists began to openly criticise the British government and make demands. They demanded that there should be elected members in the legislature with a right to discuss the budget and ask questions. The Government of India Act 1909, allowed for some elected representation.
• However, all adults were not allowed to vote. Also people could not participate in decision making under the British rule.
• But the nationalists wanted that all persons in independent India would be able to participate in making decisions.
• Therefore, when India got freedom, the dreams and aspirations of the freedom struggle were made concrete in the Constitution. The Constitution of Independent India laid down the principle of universal adult franchise. Now, all adult citizens of the country have the voting right.
• In a democractic form of government the individual or citizen is the most important person. Now the question arises how does the individual give approval to the government? One way of doing so is through elections.
• People would elect their representatives to the Parliament, then one group from among these elected representatives forms the government.
• The Parliament is made up of all representatives together and it guides the government.
• It means people through their chosen representatives form the government and control it.
• The Indian Parliament came into existence in 1947. It is the representative of the people and enjoys immense powers.
• Elections to the Paliament are held in a similar manner as they are for the state legislature.
• The Lok Sabha is usually elected once every five years. The country is divided into several constituencies. Each of these constituencies elects one person to the Parliament.
• The candidates who contest elections usually belong to different political parties. Once elected, these candidates become Members of Parliament, also known as MPs. These MPs together form the Parliament.
• The Parliament performs several functions. It selects the national government.
• The Parliament in India consists of the President, the Rajya Sabha and the Lok Sabha.
• After the Lok Sabha elections are declared, the leader of the party with majority of elected members is invited by the President to form a government. The other political parties form the opposition. The largest amongst these parties is known as the opposition party.
• Sometimes, it so happens that one political party does not get a clear majority. In such a situation a group of parties come together to form a government. Such a government is known as a coalition government.
• The Prime Minister of India is the leader of the ruling party in the Lok Sabha. From the MPs who belong to his party, the Prime Minister selects ministers to work with him to implement decisions.
• The Rajya Sabha functions primarily as the representative of the states of India in the Parliament.
• It plays an important role of reviewing and altering (alterations are required) the laws initiated by the Lok Sabha.
• The Parliament keeps a check on the ministers and their work. MPs have the right to question the ministers about the working of their departments. This is usually done during the question hour.
• The government gets valuable feedback and is kept on its toes by the questions by the MPs.
• In all matters dealing with finances, the Parliament’s approval is crucial for the government.
• The Parliament makes laws for the entire country.
• The Parliament now has more and more people from diverse backgrounds.
• There has also been an increase in political participation from the Dalit and backward castes and the minorities.
• Some seats are reserved in the Parliament for SCs and STs.
• It has also been suggested that there should be reservation of seats for women. However, this issue is still debated.

Words that Matter :

• EVM: It stands for Electronic Voting Machine.
• Approval: It refers to the formal consent through elected representatives that Parliament has as well as the fact that it needs to continue to enjoy the people’s trust.
• Representative: The person who is elected by the people is known as the people’s representative.
• Universal Adult Franchise: All adult citizens of the country enjoy the right to vote.
• Coalition: When one party does not get a clear majority, a group of political parties
form a coalition and elect a leader who then forms a government, known as coalition government.
• Parliament: The Parliament in India consists of the President, the Rajya Sabha and the Lok Sabha. It is the highest law-making body of the country. It is also known as Sansad.
• Rajya Sabha: It is also known as the Council of States. Its total membership is 245.
It is chaired by the Vice-President of India.
• Lok Sabha: It is also known as the House of the People. Its total membership is 545.
It is presided over by the Speaker.
• Opposition Party: The opposition in Parliament is formed by all the political parties that oppose the majority party or coalition formed. The largest amongst these parties is known as the opposition party.
• Ruling party: The party that rules the country.
• Unresolved: It refers to the situations in which there are no easy solutions to problems.

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A Short Monsoon Diary – CBSE Notes for Class 8 English Honeydew

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Summary:

The writer Ruskin Bond, in this diary entry tells about the silent miracles of nature and life’s little joys and regrets.
June 24 was the first day of monsoon mist. The mist was saddening. It concealed the hills and spread silence. The birds stopped singing suddenly.
June 25 brought early monsoon rain. It became warm and humid. The mist afforded some privacy also. A boy asked him to describe the hill-station and the valley in one sentence. Ruskin only said that it could have been a paradise.
On June 27, the rains marked the arrival of animals like a leopard and thousands of leeches. The leopard lifted a dog from the servants quarter below the school. Since the rains were there, the insect eating birds had no dearth of food.
All night on August 2, the rain drummed on the tin roof. But there was no shower, no thunder.
On August 3, the rain stopped and the clouds began to break up. The song of the whistling thrush emerged.
On August 12, there was endless rain and permanent mist. The writer had nowhere to go. He only looked out of the window.
On August 31, snakes and rodents rushed out of their flooded holes. They took shelter in roofs and godowns. The grandmother told the children not to kill the ‘chuchundars’ because they’ were lucky and brought money.
By October 3, the monsoon rain made way for the winter rain and snow at higher altitudes. A hailstorm in the evening hit the place. The writer was quite alone in the house. He heard only the rhythm of rain. It enveloped the house.
By March end, the winter also ended. Mussorie had black clouds over it. It hailed for half an hour. When it cleared the sky, a rainbow was formed across it.

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The Great Stone Face – I – CBSE Notes for Class 8 English Honeydew

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Summary:

The Great Stone Face was the work of nature. It was formed on the side of a mountain by some rocks. Seen from a distance they looked like a human face and alive. Going near, the face turned into a heap of rocks. The people believed that the valley owed much of its fertility to that face.
One day a mother and her little child, Ernest sat at the door of their cottage. He wished that the Great Stone Face could speak. The mother hoped to see a man some time with a similar face. She told a curious stray, she herself had heard in her childhood. A great man bearing that stone face would be born some day. That was a prophecy.
Ernest could never forget that story. He was very helpful to his mother. He grew up to be a gentle, quiet young man. The Stone Face became his teacher. The child used to watch it for hours.
Once a rumour spread that the great man, who was to bear a resemblance to the Great stone face, had appeared at last. Many years ago, a young man had left the valley and settled at a distant sea port. He became very rich. Then he decided to return to his native place. He was Mr. Gathergold. People welcomed him as the great man because he resembled the great stone face. But Ernest didn’t agree with these people.
Years went on. Ernest grew to be a young man. He drew little attention. He had nothing remarkable. But he was hardworking and kind. He still loved to gaze upon the great stone face. He wondered why the stone faced man was taking so long in coming to that valley.
Mr. Gathergold died as a poor man and was buried. People then agreed that there was no likeness between the mined merchant and the majestic face upon the mountain.
It so happened that another son of the valley returned to his native valley. He had become a famous commander. The people turned to him blindly and accepted him as the Great Stone Face. But Ernest could not see any similarity between them.

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