In the major resonance structure for the cyanide ion (CN^-), which atom carries the negative formal charge?

• A. Both carbon and nitrogen
• B. Nitrogen
• C. Neither atom
• D. Carbon

Answer: (B)

Verified step by step guidance

1. Recall that the cyanide ion (CN⁻) consists of one carbon atom and one nitrogen atom connected by a triple bond, with an overall negative charge.
2. To determine which atom carries the negative formal charge in the major resonance structure, calculate the formal charge on each atom using the formula: \[\text{Formal Charge} = \text{Valence Electrons} - \text{Nonbonding Electrons} - \frac{1}{2} \times \text{Bonding Electrons}\]
3. For carbon, count its valence electrons (4), the number of lone pair electrons it has, and the bonding electrons it shares with nitrogen. Do the same for nitrogen (valence electrons = 5).
4. Compare the formal charges calculated for carbon and nitrogen. The major resonance structure is the one where the negative charge is on the more electronegative atom, which is nitrogen in this case.
5. Conclude that in the major resonance structure of CN⁻, the nitrogen atom carries the negative formal charge because it is more electronegative and stabilizes the negative charge better than carbon.