Which of the following species is not paramagnetic?

Step-by-step solution

CO has no unpaired electron while other have unpaired electrons so, paramagnetic in nature.(Apply M.O.T) Molecular orbital configuration ⇒ CO  : like N 2   ;  σ 1 s 2 < σ * 1S 2 < σ 2 S 2 < σ * 2 S 2 < π 2 P x 2 = π 2 P y 2 < σ 2 P z 2     ( No unpaired electrons) O 2   : σ 1 S 2 < σ * 1S 2 < σ 2 S 2 < σ * 2 S 2 < σ 2 P z 2 < π 2 P x 2 = π 2