Question

The correct order of stabilities of the following resonance structures is:

(I) $H_2C-\overset{\ominus}{N}\equiv \overset{\oplus}{N}$ (II) $H_2\overset{\oplus}{C}=N-\overset{\ominus}{N}$

(III) $H_2\overset{\ominus}{C}-N= \overset{\oplus}{N}$ (IV) $H_2\overset{\oplus}{C}-N= \overset{\ominus}{N}$

• A. I > II > IV > III
• B. I > III > II > IV
• C. II > I > III > IV
• D. III > I > IV > II

Answer 1

Answer: (A)

I > II > IV > III

Answer 2

To determine the stability of resonance structures, we follow a set of rules in decreasing order of importance:

1. Octet Rule: Structures where all atoms (especially C, N, O) have complete octets are generally the most stable.
2. Number of Covalent Bonds: Structures with a greater number of covalent bonds are more stable.
3. Charge Separation: Structures with less charge separation are more stable. If charges are present, structures with minimal charge separation are preferred.
4. Electronegativity: Negative charge on a more electronegative atom and positive charge on a less electronegative atom is more favorable.
5. Adjacent Charges: Structures with like charges on adjacent atoms are highly unstable.

Applying these rules, the stability order is I > II > IV > III.