JEE Main · 2022 · 26 Jun 2022 · Shift 2 · Chemical Bonding and Molecular Structure

Among the nitrogen oxides, $\mathrm{NO}{}_2$ (nitrogen dioxide) contains an unpaired electron on the nitrogen atom, making it a free radical.

The Lewis structure of $\mathrm{NO}{}_2$ shows nitrogen with one unpaired electron, which accounts for its paramagnetic nature and tendency to dimerize to form $\mathrm{N}{}_2\mathrm{O}{}_4$.

The other oxides:

• $\mathrm{N}{}_2\mathrm{O}$: all electrons paired
• $\mathrm{N}{}_2\mathrm{O}{}_3$: all electrons paired
• $\mathrm{N}{}_2\mathrm{O}{}_5$: all electrons paired

Therefore, $\mathrm{NO}{}_2$ is the oxide with an odd electron at the nitrogen atom.