Q. Four diatomic species are listed below in different sequences. Which of these presents the correct order of their increasing bond order?
A) He₂⁺ < O₂⁻ < NO < C₂²⁻
B) O₂⁻ < NO < C₂²⁻ < He₂⁺
C) NO < C₂²⁻ < O₂⁻ < He₂⁺
D) C₂²⁻ < He₂⁺ < NO < O₂⁻
Explanation
[Solution from source] From MO theory: He₂⁺ (3 e⁻) has bond order 0.5, O₂⁻ (17 e⁻) 1.5, NO (15 e⁻) 2.5, and C₂²⁻ (14 e⁻, like N₂) 3. The increasing order is He₂⁺ < O₂⁻ < NO < C₂²⁻. Placing He₂⁺ last mistakes its weak half bond for a strong one. Answer (1).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.