Chemical Bonding & Molecular Structure

Concept:The ONO bond angle is determined by the steric number and lone pairs on the central nitrogen atom, based on VSEPR theory.Explanation:First, find the hybridisation and molecular geometry of each species.For $\mathrm{NO}_2^+$: nitrogen is $sp$ hybridised, linear shape, bond angle $180^\circ$.For $\mathrm{NO}_2$: nitrogen is $sp^2$ hybridised with one unpaired electron (acts like a lone pair), bent shape, angle slightly less than $120^\circ$ (about $134^\circ$).For $\mathrm{NO}_2^-$: nitrogen is $sp^2$ hybridised with one lone pair, bent shape, angle less than $120^\circ$ (about $115^\circ$).For $\mathrm{NO}_3^-$: nitrogen is $sp^2$ hybridised, trigonal planar, bond angle $120^\circ$.Thus, increasing order of ONO bond angle is: $\mathrm{NO}_2^- < \mathrm{NO}_3^- < \mathrm{NO}_2 < \mathrm{NO}_2^+$.This matches option B.Answer:Option B: $\mathrm{NO}_2^- < \mathrm{NO}_3^- < \mathrm{NO}_2 < \mathrm{NO}_2^+$