Question

Which of the following species is paramagnetic?

• A. $O_2^{-}$
• B. $C{N}^{-}$
• C. CO
• D. $N{O}^{+}$

Answer 1

The correct option is A $O_2^{-}$

Using MOT, we can find magnetic behaviour of compounds.
Number of electrons in $O_2^{-},C{N}^{-},CO,N{O}^{+}$ are 17, 14, 14, 14 respectively.
$O_2^{+}$ =$(\sigma 1s{)}^2<(\sigma 1s^{\ast }{)}^2<(\sigma 2s{)}^2<(\sigma 2s^{\ast }{)}^2<(\sigma 2p_z{)}^2<(\pi 2p_x=\pi 2p_y{)}^4<(\pi 2p_x^{\ast }=\pi 2p_y^{\ast }{)}^3$
$O_2^{+}$ is paramagnetic