Previous Year NEET Question- Chemical Bonds L-6

Question: The $\mathrm{BCl}_3$ is a planar molecule whereas $\mathrm{NCl}_3$ is pyramidal because#

A) nitrogen atom is smaller than boron atom

B) $\mathrm{BCl}_3$ has no lone pair but $\mathrm{NCl}_3$ has a lone pair of electrons

C) $\mathrm{B}-\mathrm{Cl}$ bond is more polar than $\mathrm{N}-\mathrm{Cl}$ bond

D) $\mathrm{N}-\mathrm{Cl}$ bond is more covalent than $\mathrm{B}-\mathrm{Cl}$ bond.

Answer: $\mathrm{BCl}_3$ has no lone pair but $\mathrm{NCl}_3$ has a lone pair of electrons#

Solution:#

There is no lone pair on boron in $\mathrm{BCl}_3$ hence, no repulsion takes place. There is a lone pair on nitrogen in $\mathrm{NCl}_3$ hence, repulsion takes place. Therefore, $\mathrm{BCl}_3$ is planar molecule but $\mathrm{NCl}_3$ is pyramidal molecule.