Which of the following is paramagnetic?
- CN-
- NO+
- CO
- O2-
Answer
(4) O2-
Solution
CN-, NO+ and CO each have 14 electrons ⇒ all electrons paired ⇒ diamagnetic.
O2- has 17 electrons:
1s2 *1s2 2s2 *2s2 2pz2 2px2 = 2py2 *2px2 = *2py1
⇒ one unpaired electron ⇒ paramagnetic.
Answer: (4)