Four diatomic species are listed below. Identilfy the correct order in which the bond order is increasing in them:

Options

(a) NO (b) O₂⁻ (c) C₂²⁻ (d) He₂⁺

Correct Answer:

He₂⁺ Explanation:

Bond order = Nₙ – Nₘ / 2
He₂⁺ = σ(1s)² σ*(1s) B.O. = 0.5
O₂⁻ = KKσ(2s)² σ*(2s)² σ(2pₖ)²
π(2pᵢ)² π(2pⱼ)² π*(2pᵢ)² π*(2pⱼ)¹ B.O. = 1.5
NO = KKσ(2s)² σ*(2s)²π(2pᵢ)²
π(2pⱼ)² σ(2pₖ)² π*(2pᵢ)¹ B.O. = 2.5
C₂²⁻ = KKσ(2s)² σ*(2s)²π(2pᵢ)² π(2pⱼ)² σ(2pₖ)² B.O. = 3.0