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Chemical Bonding:
Summary:
• Chemical bonding is the attractive force which holds the atoms or ions
together in a chemical species
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Molecule is an
electrically neutral cluster of mutually bounded atoms
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e
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Octet rule is
the tendency of an atom of the elements to have eight electrons in its
valence shell
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Electrovalence is the
number of electrons lost or gained by an atom of the element during the
formation of ionic bond
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Covalent bond: It is the bond formed by equal contribution and mutual
sharing of electrons between two atoms
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Covalent compounds are the
compounds containing covalent bonds
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Bond pair of electrons
is the pair of electrons shared between two atoms
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Co-ordinate bond or dative bond: It is a special case of covalent bond
formed between two atoms in which both the electrons are contributed

by one of the atoms whereas the other atom simply takes part in
sharing
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Reduction is a chemical process in which an atom or an ion gains one or
more electrons
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Questions and solutions:
1
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(a) State which one is (1) a non-metal (2) a metal (3) chemically inert
(b) Write down the formula of compound formed by two of the above
elements?
Ans
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2
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In the solid state, there are strong electrostatic forces of attraction
between the oppositely charged ions and ions cannot move, hence do not
conduct electricity
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A compound has the formula H2Y (Y = Non-metal)
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(b) the valency of Y
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Ans
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(b) 2
(c) Covalent

4
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Ans
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5
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Which
one:
(a) forms an anion?
(b) forms an cation?
(c) has four electrons in its valence shell?
Ans
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Electronic configuration

X

6

2,4

Y

9

2,7

Z

12

2,8,2

(a) Y will form an anion
(b) Z forms a cation
(c) X has four electrons in its valence shell
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Define covalent bond
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The bond formed by equal contribution and mutual sharing of electrons
between two atoms so that both the atoms acquire the stable nearest noble
gas configuration i
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, get their octet complete is called covalent bond
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Define electrolysis
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It is defined as the process of chemical decomposition of an electrolyte
present in the molten or dissolved state, by passing electric current through it
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On the basis of knowledge of electronic configuration of elements,
predict the nature of bonds in each of the following molecules
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Molecule

Nature of bond

N2

Covalent bond

CO2

Covalent bond

HCl

Covalent bond

MgCl2

Ionic bond

CCl4

Covalent bond

HCN

Covalent bond

9
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Hydronium ion

b
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a
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b
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10
...

Ans
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11
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(a) Ionic bond
(c) Ionic bond

(c) 11 and 16

(e) 8 and 16
(b) covalent bond
(d) Covalent bond (e) Covalent bond
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Why do atoms combine?
Ans
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e
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13
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It has been found that a methane molecule has a three dimensional
tetrahedral structure
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In such a configuration, none of the
participating atom is more electrically charged as compared to other atoms
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14
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The atoms attain noble gas configuration by losing, gaining or sharing of
electrons present in their valence shells
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What is lone pair effect? In what kind of compound does this effect
occur?
Ans
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Lone pair effect is shown by polar covalent compounds such as HCL and
NH3
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What are the conditions for formation of an electrovalent bond?
Ans
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(2) High electron affinity: The other atom should have high electron affinity
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17
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Ans
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Colour

Sodium atom (Na)
Silvery white

Sodium ion (Na+)
Colourless

2
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Action with water

Very reactive

No action with water

4
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(a) Name two compounds that are covalent when take pure but produce
ions when dissolved in water
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Ans
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(b) HCl + H2O = H3O+ + ClHBr + H2O = H3O+ + Br19
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Give two limitations of this rule
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This is called octet rule
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, in which the central atom has more than eight electrons in its valence
shell
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20
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(a) Ionic bond
(b) Both ionic and covalent bonds
(c) Both ionic and covalent bonds
(d) Covalent bond
(e) Ionic bond
(f) Both ionic and covalent bonds
(g) Ionic bond
(h) Covalent bond
(i) Covalent bond
(j) Covalent bond
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Elements X is a metal with a valency 2
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(1) Write equations to show how X and Y form ions
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(3) If the compound formed between X and Y is melted and an electric current
passed through the molten compound, the element X will be obtained at the
………………
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(Provide the missing words)
Ans
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Five atoms labelled A to E have mass numbers and atomic numbers as
given below
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(a) E contains 7 protons
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(d) (1) A and C are metals
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23
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(a) What type of chemical bond is present in X
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(c) Will it be a good conductor of electricity or not?
(d) Will it dissolve in organic solvent or not?
Ans
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(d) Yes, because it is a non-polar compound so it will dissolve in non-polar
solvents
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In the formation of compound XY2, atom X gives one electron to each Y
atom
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Ans
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Properties:
•
•
•
•

It is hard and brittle
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It has high melting and boiling point
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25
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(1) B (2) A
26
...

Ans
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NaCl
Soluble in water
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Give suitable chemical term for the following :
A bond formed by a shared pair of electrons with both electrons coming from
the same atom
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Coordinate bond
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Which of the following is not a typical property of an ionic compound?
(a) High melting point
(b) Conducts electricity in the molten and in the aqueous solution state
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(d) They exist as oppositely charged ions even in the solid state
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c
29
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(a) Ammonia

(b) Ammonium chloride
(c) Sodium hydroxide
(d) Calcium Chloride
Ans
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Why pure HCl is a bad conductor of electricity?
Ans
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31
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Because it is a non polar covalent compound
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Why solution of cane sugar does not conduct electricity?
Ans
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33
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Because hydrogen has one proton and one electron in it, when it loses one
electron it is left with a proton only and hence it is named as a proton
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Which of the following does not represent oxidation:
(a) Loss of electrons

(b) Addition of oxygen

(c) Addition of hydrogen

(d) Increase in oxidation number
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c
35
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b
36
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a
37
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d
38
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d
39
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a
40
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a
41
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Atomic No
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Which element has 3 shells?
b
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Compound formed between A and B?
d
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Element having 3 valency?
F
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a
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C2

c
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D

e
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A

42
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a
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Which substance in the list is an example of a non polar molecule?
c
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Which substance in the list is an example of giant structures of ions?
e
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a
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Methane

d
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Diamond

c
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An aqueous solution of sodium chloride conducts electricity
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An aqueous solution of sodium chloride contains electricity because water
is polar solvent and has a high dielectric constant which leads to formation of
sodium and chloride ions which conduct electricity
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Fill in the blanks:

a
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Of
electrons
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Electrovalent compounds have a ………… boiling point
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A molecule of ……………
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Ans
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Sharing

b
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nitrogen
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Why are ionic compounds crystalline solids?
Ans
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As the ions are not free to move in any
direction, therefore, on the whole an ionic compound is a hard crystalline solid
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What is dielectric constant?
Ans
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47
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Explain?
Ans
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48
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Column A

Column B

1
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Increases

2
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Covalent bond

3
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Ionic bond

Period
4
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Covalent and co-ordinate

Down the group

bond

5
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Decreases

Ans
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Ionic bond
2
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Increases
4
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Covalent bond
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What are non-polar and polar covalent bonds?
Ans
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Such a covalent bond is called non-polar covalent bond
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g
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When a covalent bond is formed between two atoms having different
electronegativities, the shared pair of electrons is attracted more towards the
atom having higher electronegativity
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Such covalent bond is called
polar covalent bond
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A greenish gas with single covalent bond?
Ans
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