JEE Main · 2024 · 04 Apr 2024 · Shift 1 · Chemical Bonding and Molecular Structure

$\mathrm{C}{\mathrm{H}}_4$ (tetrahedral) and $\mathrm{P}{\mathrm{F}}_5$ (trigonal bipyramidal) are symmetric, so their net dipole moment is zero.

For the two pyramidal molecules, compare $\mathrm{N}{\mathrm{H}}_3$ and $\mathrm{N}{\mathrm{F}}_3$. In $\mathrm{N}{\mathrm{H}}_3$ the resultant of the N–H bond dipoles and the lone-pair moment point the same way and add. In $\mathrm{N}{\mathrm{F}}_3$ the N–F bond dipoles point opposite to the lone-pair moment and partly cancel. Hence

Maximum dipole moment: $\mathrm{N}{\mathrm{H}}_3$ $\Rightarrow$ option C.