$B.O = \frac{{10 - 4}}{2} = 3$ (diamagnetic)

$N_2^{2 - } - {\sigma _{1s}}2{\sigma ^*}_{1s}2{\sigma _{2s}}2{\sigma ^*}_{2{s^2}}[{\pi _{2p_x^2}} = {\pi _2}p_y^2]{\sigma _{2p_z^2}}[{\pi _{2p_x^1}} = {\pi ^*}_{2p_y^1}]$

$B.O = \frac{{10 - 6}}{2} = 2$ (paramagnetic)

$O_2^{2 - } - {\sigma _{1s}}2{\sigma ^*}_{1s}2{\sigma _{2s}}2{\sigma ^*}_{2s}2{\sigma _{2p_z^2}}[{\pi _{2p_x^2}} = {\pi _2}p_y^2]\,[{\pi _{2p_x^2}} = {\pi ^*}_2p_y^2]$

$B.O = \frac{{10 - 8}}{2} = 1$ (diamagnetic)

${O_2} - {\sigma _{1s}}2{\sigma ^*}_{1s}2{\sigma _{2s}}2{\sigma ^*}_{2s}2{\sigma _{2p_z^2}}\,[{\pi _{2p_x^2}} = {\pi _2}p_y^2]\,[{\pi _{2p_x^2}} = {\pi ^*}_2p_y^2]$

$B.O = \frac{{10 - 6}}{2} = 2$ (paramagnetic)