Chemistry - CHEMICAL BONDING Question with Solution | TestHub

Electronegativity difference between $\mathrm{N}(3.0)$ and $\mathrm{Cl}(3.0)$ is zero and hence, $\mathrm{N}-\mathrm{Cl}$ bonds are non-polar. As a result, the overall dipole moment of ${\mathrm{NCl}}_3$ molecule and its direction is just the dipole moment of the lone pair of electrons.
On the other hand, $\mathrm{N}-\mathrm{Br}(3.0-2.8)$, $\mathrm{N}-1(3.0-2.5)$ and $\mathrm{N}-\mathrm{H}(3.0-2.1)$ are polar and hence, contribute towards the overall dipole moment of the respective molecules. Since the EN difference is highest in case of $\mathrm{N}-\mathrm{H}$ bonds, therefore, ${\mathrm{NH}}_3$ has the highest dipole moment.