In NH₃ and NF₃, the difference in electronegativity is nearly same but the dipole moment of NH₃ = (1.46D)
For Example, NF₃ = (0.24D)
In NH₃, the dipole moments of the three N - H bonds are in the same direction as the lone pair of electron. But in NF₃, the dipole moments of the three N.- F bonds are in the direction opposite to that of the lone pair. Therefore, the resultant dipole moment in NH₃ is more than in NF₃

In BF₃ , there are 3 bond pairs 0 lone pair, so boron is sp² hybridised and in NH₃, there are 3 bond pairs and 1 lone pair, so nitrogen is sp³ hybridised. After the reaction hybridisation of boron changes to sp³ but hybridisation of nitrogen remains the same becuase N shares its lone pair with electron deficient B.

Electronic configuration of Be₂ molecule (4 + 4 = 8) 
σ1s²,σ1s²,σ1s²,σ1s²
Bond order=1/2[Nb−Na]=1/2(4−4)=0
Since, bond order in zero, so Be₂ does not exist.

The single Lewis structure based on the presence of two single bonds and one double bond between carbon and oxygen atoms is inadequate to represent the molecule accurately as it represents unequal bonds. According to the experimental findings, all carbon to oxygen bonds in \(\mathrm{CO}_{3}^{2-}\) are equivalent. Therefore the carbonate ion is best described as a resonance hybrid of the canonical forms I, II, and III shown below.

Resonance in \(\mathrm{CO}_{3}^{2-}\) I, II and III represent the three canonical forms.

(a) AgI is more covalent that AgCl. This is because I^- ion is larger in size than Cl^- ion and hence, is more polarised than Cl ion.^-
(b) BeCl₂ is more covalent than MgCl₂ . This is because Be²⁺ ion is smaller in size than Mg²⁺ ion and hence has the greater polarising power.
(c) SnCl₄ is more covalent than SnCl₂ . This is because Sn⁴⁺ ion has greater charge and smaller size than Sn²⁺ ion and hence has greater polarising power.
(d) CuS is more covalent than CuO. This is because S^2- ion has larger size than O^2- ion and hence is more polarised than O^2- ion.

1.(c) H₂O has lone pairs causing bent shape
Explanation: Bent shape causes dipoles not to cancel → net polarity in H₂O
2.(a) Boiling point
Explanation:Polar molecules have stronger intermolecular forces (H-bonding) → higher boiling point.
3.(d) 104.5°
Explanation: Due to 2 lone pairs on oxygen → more repulsion → bond angle reduced to 104.5°

(a) Assertion is correct, reason is correct; reason is a correct explanation for assertion.
Explanation:
While the lone pairs are localised on the central atom, each bonded pair is shared between two atoms. As a result, the lone pair electrons in a molecule occupy more space as compared to the bonding pairs of electrons. This results in greater repulsion between lone pairs of electrons as compared to the lone pair -bond pair and bond pair – bond pair repulsions.