The bond order and magnetic characteristics of ${\mathrm{CN}}^{-}$ are :

${\mathrm{CN}}^{-}$is a 14 electron system. The bond order and magnetism can be predicted using MOT. The MOT electronic configuration of ${\mathrm{CN}}^{-}$is:
${\mathrm{\sigma }}_{1 \mathrm{s}}^2{\mathrm{\sigma }}_{1 \mathrm{s}}^{*2}{\mathrm{\sigma }}_{2 \mathrm{s}}^2{\mathrm{\sigma }}_{2 \mathrm{s}}^{*2}\left({\mathrm{\pi }}_{2{\mathrm{p}}_{\mathrm{x}}}^2={\mathrm{\pi }}_{2{\mathrm{p}}_{\mathrm{y}}}^2\right){\mathrm{\sigma }}_{2{\mathrm{p}}_{\mathrm{z}}}^2$

Bond order $=1/2\left({\mathrm{N}}_{\text{bonding }}-{\mathrm{N}}_{\text{antibonding }}\right)=3$
As ${\mathrm{CN}}^{-}$does not have any unpaired electrons, and hence it is diamagnetic.