Question

Which of the following is correct, based on molecular orbital theory for peroxide ion?

• A. Its bond order is one and it is paramagnetic
• B. Its bond order is two and it is diamagnetic
• C. Its bond order is one and it is diamagnetic
• D. Its bond order is two and it is paramagnetic

Hint:

Peroxide ($O_{2}^{2-}$) has 18 electrons; all are paired.

Answer 1

The Correct Option is C

Step 1: Concept
Apply Molecular Orbital (MO) theory to the peroxide ion ($O_{2}^{2-}$).
Step 2: Analysis
Configuration: $KK(\sigma 2s)^{2}(\sigma^{*} 2s)^{2}(\sigma 2p_{z})^{2}(\pi 2p_{x})^{2}(\pi 2p_{y})^{2}(\pi^{*} 2p_{x})^{2}(\pi^{*} 2p_{y})^{2}$.
Bond Order = $\frac{8 - 6}{2} = 1$.
Step 3: Conclusion
As all electrons are paired in the orbitals, the ion is diamagnetic.
Final Answer: (C)