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Lone pair of Electrons – are a pair of electrons not shared with any other atom.

The atoms transfer or share electrons so that all the atoms involved in chemical bonding obtain eight electrons in their outer shell (valence shell). It is called octet rule.

Electronic configuration of non-metallic element (say X) with atomic number 9 is ; 

K L

X (Z = 9): 2, 7

Thus it requires one electron to complete its octet and attain stable structure of nearest noble gas (Ne). To do this each of the two ‘X’ atoms contributes one electron so as to have one shared pair of electrons between them. Both atoms attain stable doublet structure, resulting in the formation of a single covalent bond between them as shown below:

Ammonia – Polar covalent compoun

 …..

When a molecule of ‘NH₃’ is to be formed – One atom of nitrogen shares three electron pairs one with each of the three atoms of hydrogen.

Formation of Ammonia Molecule can be represented by Atomic or orbit structural diagram

......…. 

The interatomic attractive forces which holds the constituent atoms/ions together in a molecule are called chemical bonds.

Covalent compounds are formed by sharing electron pairs between non-metallic atoms. Non-metallic atoms having 7,6, 5 valence electrons (4, 5, 6, 7) share one, two or three pairs of electrons respectively. 

Answer is 2,8,7

Shorter

Double bonds as compared to single bonds are Shorter.

Single bonds are formed by sharing one pair of electrons. It is represented by a small line between the symbols of the combining element,

eg. Fluorine molecules can be represented as F – F. The atomic number of chlorine is 17.

In covalent compounds, the bond is formed due to sharing of electrons. 

2  electrons are accepted by oxygen

Electron sharing

The chemical bond formed as a result of the sharing of electrons between the combining atoms is called a covalent bond.

1. one pair

2. 1

One pair of electrons are shared

(a) Co-ordinate bond.

(b) Covalent bond.

Bond order (B.O) = \(\frac{1}{2}\) × [Number of an electron in antibonding molecular orbitals] – [Number of electrons in bonding molecular orbitals]

B.O for O₂^2- = \(\frac{1}{2}\) × [10 – 8] = \(\frac{1}{2}\) × 2

B.O for O₂^2- = 1

a) One pair of electrons 

b) H – Cl

The correct answer is (i) 2s²2p⁵

Double and triple bonds are multiple bonds.

B) both (ii) and (iv)

The hypothetical line joining the centre of nuclei of two atoms in a molecule.

Correct option is  B) Oxygen

A covalent bond in a heteroatomic molecule. 

Eg : HCl.

 Correct option is  A) Fluorine

An atom with low ionization potential and another with high electron affinity.

Correct option is: B) Oxygen

In the formation of covalent bond electrons are mutually shared between atoms of elements.

A) I-A and VII-A

Correct option is: A) +1

Correct option is  A) +1

The attractive force which binds hydrogen atom of one molecule with electronegative atom present is the same or other molecule is called hydrogen bond.

D) Coordination number

G. A. Perkin in 1921.

B) Ionic bond

D) All of these

 Correct option is  B) 1s² 2s² 2p⁶

D) all of these

(iv) A and R both are false.

If two electrons are present in valence shell, then it is called doublet configuration. 

Eg.: Helium exhibits doublet configuration.

(b) Both (A) and (R) are correct but (R) is not the correct explanation of(A).

1. The bonding in metal is explained by molecular orbital theory. As per this theory. the atomic orbitals of large number of atoms in a crystal overlap to form numerous bonding and anti-bonding molecular orbitals without any band gap.

2. The bonding molecular orbitals are completely filled with an electron pair in each, and the anti-bonding molecular orbitals are empty.

3. Absence of band gap accounts for high electrical conductivity of metals.

(c) Fluorine

Most metals are black except copper, silver and gold. It is due to the absorption of light of all wavelengths. Absorption of light of all wavelengths is due to the absence of band gap in metals.

(c) Non metals

(d) N₂

Solution:

N ≡ N

The correct option is- (b) 1.54Å

The correct option is- (d) l.33A