Number of molecules/species from the following having one unpaired electron is . O2, O2-1, NO, CN-1, O22-
Answer
2
Solution
MOT — count electrons in the antibonding *2p orbitals:
O2 (16 e): *2px1 *2py1 ⇒ 2 unpaired
O2- (17 e): *2px2 *2py1 ⇒ 1 unpaired ✓
NO (15 e): *2px1 ⇒ 1 unpaired ✓
CN- (14 e, like N2): all paired ⇒ 0
O22- (18 e): * full ⇒ 0
∴ O2- and NO ⇒ 2
Answer: 2