$\mathrm{BCl}_{3}$ is a planar molecule whereas $\mathrm{NCl}_{3}$ is pyramidal because

$\mathrm{BCl}_{3}$ is a planar molecule whereas $\mathrm{NCl}_{3}$ is pyramidal because
  1. $\mathrm{BCl}_{3}$ has no lone pair of electrons but $\mathrm{NCl}_{3}$ has a lone pair of electrons.
  2. $\mathrm{B}-\mathrm{Cl}$ bond is more polar than $\mathrm{N}-\mathrm{Cl}$ bond.
  3. nitrogen atom is smaller than boron atom.
  4. $\mathrm{N}-\mathrm{Cl}$ bond is more covalent than $\mathrm{B}-\mathrm{Cl}$ bond.

Solution

In $\mathrm{BCl}_{3}$ there is $\mathrm{sp}^{2}$ hybridisation (planar) whereas in $\mathrm{NCl}_{3}$ hybridisation is $s p^{3}$ hence shape is pyramidal

Asked in: JEE-TOPICTESTS-CHEMISTRY

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