JEE Main · 2026 · 22 Jan 2026 · Shift 2 · Chemical Bonding and Molecular Structure

Comparing the dipole moments, ${\mathrm{H}}_2\mathrm{O}$ ($1.85$ D), $\mathrm{N}{\mathrm{H}}_3$ ($1.47$ D), $\mathrm{CHC}{\mathrm{l}}_3$ ($\sim 1.0$ D) and ${\mathrm{H}}_2\mathrm{S}$ ($\sim 0.95$ D) are all appreciable, whereas in $\mathrm{N}{\mathrm{F}}_3$ the resultant of the three polar $\mathrm{N}-\mathrm{F}$ bond dipoles opposes the dipole of the nitrogen lone pair, leaving a very small net moment ($0.23$ D). Hence the molecule X of lowest dipole moment is $\mathrm{N}{\mathrm{F}}_3$, a pyramidal molecule in which the central nitrogen uses three bond pairs and keeps one lone pair. The number of lone pairs on the central atom is $1$.