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CSS Physical and Inorganic Chemistry P-I QUESTION #1433
Question 1
According to molecular orbital theory, the bond order of \(\text{O}_2^{-}\) is:
  • 1.0
  • 1.5✔️
  • 2.5
  • None of these
Correct Answer Explanation
The MO electron configuration of O\(_2\) (16e\(^-\)): \(\sigma_{1s}^2\sigma_{1s}^{*2}\sigma_{2s}^2\sigma_{2s}^{*2}\sigma_{2p}^2\pi_{2p}^4\pi_{2p}^{*2}\). Bond order of O\(_2 = \frac{8-4}{2}=2\). O\(_2^-\) has one extra electron: \(\pi_{2p}^{*3}\), so bonding electrons = 8, antibonding = 5. Bond order \(= \dfrac{8-5}{2} = \dfrac{3}{2} = 1.5\).