JEE Main · 2025 · 29 Jan 2025 · Shift 2 · Chemical Bonding and Molecular Structure

The total valence-electron count for $N{O}_2^{-}$ is $5(N)+2\times 6(O)+1(\text{charge})=18$. Drawing the Lewis structure, nitrogen forms one $N=O$ and one $N-O$ bond, using three bonding pairs (6 electrons) shared across the three atoms. This leaves $18-6=12$ electrons as lone pairs — one lone pair on nitrogen and the rest distributed over the two oxygens. $N{O}_2^{-}$ has 12 non-bonded electrons.