Question

The bond order and magnetic characteristics of $C{N}^{-}$ are:

• A. 3, paramagnetic
• B. 2.5, diamagnetic
• C. 3, diamagnetic
• D. 2.5, paramagnetic

Answer 1

The correct option is C 3, diamagnetic

$C{N}^{-}$ is a 14 electron system. The bond order and magnetism can be predicted using MOT.

The MOT electronic configuration of $C{N}^{-}$ is:

$\left({\sigma }_{1s}{)}^2\right({\sigma }_{1s}^{\ast }{)}^2\left({\sigma }_{2s}{)}^2\right({\sigma }_{2s}^{\ast }{)}^2\left({\pi }_{2p_x}{)}^2\right({\pi }_{2p_y}{)}^2({\sigma }_{2p_z}{)}^2$

Bond order $=\frac{1}{2}\times (N_{bonding}-N_{antibonding})=3$

As $C{N}^{-}$ does not have any unpaired electrons, and hence it is diamagnetic.