What is the effect of the following processes on the bond order in $\mathrm{N}_{2}$ and $\mathrm{O}_{2}$ ?

$(A)$ ${{\rm{N}}_2} \to {\rm{N}}_2^ +  + {{\rm{e}}^ – }$

$(B)$ ${{\rm{O}}_2} \to {\rm{O}}_2^ +  + {{\rm{e}}^ – }$

The molecular orbital configuration of a diatomic molecule is

$\sigma \,\,1{s^2}\,\,{\sigma ^*}\,\,1{s^2}\,\sigma \,\,2{s^2}\,{\sigma ^*}\,2{s^2}\,\,\sigma \,2p_x^2\,\left\{ {{}_{\pi \,2p_z^2}^{\pi \,2p_y^2}} \right.$ 

Its bond order is

Assertion : $B_2$ molecule is diamagnetic.
Reason : The highest occupied molecular orbital is of $\sigma $ type.

Which of the following diatomic molecular species has only $\pi$ bonds according to Molecular Orbital Theory?

Among the following species$N _{2}, N _{2}^{+}, N _{2}^{-}, N _{2}{ }^{2-}, O _{2}, O _{2}{ }^{+}, O _{2}^{-}, O _{2}{ }^{2-}$ the number of species showing diamagnetism is.