Question

Azide ion ($N_3^{-}$) exhibits on $N-N$ bond order of $2$ and may be represented by resonance structures, I, II and III given below. Select correct statements.

• A. Structures I and II make greater contributions than III
• B. Structures II and III make greater contributions than I
• C. Structures I and III make greater contributions than II
• D. All the above three structures make equal contributions.

Answer 1

The correct option is B Structures II and III make greater contributions than I

$:\stackrel{\ominus }{\underset{..}{N}}=\stackrel{+}{N}=\stackrel{-}{\underset{..}{N}}:⟷:\stackrel{..}{\underset{..}{N}}-\stackrel{+}{N}\equiv N:⟷:N\equiv \stackrel{+}{N}-\stackrel{..}{\underset{..}{N}}:$ out of all these 3, the 1 also called resonance hybrid has exceptional stablization and unique properties.

A destabilizing factor is present in two azides canonical form 2 and 3. each of these 2 structures has 3 bonds, whereas 1 has 4 bonds.

The destablizing resonating structure would want to become stable by welcomig the $N\equiv N$ as $N_2$ gas.

Since I is stable, it is less likely to be reactive than 2 and 3 are unstable, therefore would be greater contribution (by being reactive ) compound to I.