Total electron

$NO^+$                     $14$

$CO$                         $14$

$O_2^{2-}$                        $18$

$B_2$                          $10$

$N{O^ + } \Rightarrow KK.\sigma {(2s)^2}{\sigma ^*}{(2s)^2}.{(\pi 2{p_x})^2}$

          $ = {(\pi 2{p_y})^2}.{(\sigma 2{p_z})^2}$ diamagnetic

$CO \Rightarrow KK.\sigma {(2s)^2}{\sigma ^*}{(2s)^2}.{(\pi 2{p_x})^2}$

          $ = {(\pi 2{p_y})^2}.{(\sigma 2{p_z})^2}$ diamagnetic

$O_2^{2 – } \Rightarrow KK.\sigma {(2s)^2}{\sigma ^*}{(2s)^2}.\sigma {(2{p_z})^2}{(\pi 2{p_x})^2}$

         $ = {(\pi 2{p_y})^2}.{\pi ^*}{(2{p_x})^2} = {\pi ^*}{(2{p_y})^2}$ diamagnetic

${B_2} \Rightarrow KK.\sigma {(2s)^2}{\sigma ^*}{(2s)^2}.\pi {(2{p_x})^1} = \pi {(2{p_y})^1}$   paramagnetic