JEE Main 2025 Jan 29 Shift 2, Chemistry Q25: Important Concepts Of Chemical Bonding

Total valence electrons in $N{O}_2^{-}$: $N(5)+2\times O(6)+1(\text{negative charge})=18$ electrons.

Draw the Lewis structure: one $N=O$ double bond, one $N-O$ single bond (with the negative charge on the singly-bonded oxygen), and one lone pair on nitrogen.

Bond pairs: one $\sigma$ + one $\pi$ (double bond) + one $\sigma$ (single bond) $=3$ bond pairs $=6$ bonding electrons.

Non-bonding electrons $=18-6=12$.

Distribution check: $N$ has $2$ (one lone pair), $=O$ has $4$ (two lone pairs), $-O^{-}$ has $6$ (three lone pairs); total $=2+4+6=12$. $✓$

$\therefore$ Number of non-bonded electrons $=12$.