$\mathrm{O}_{2}^{-}=\left(\sigma_{1 \mathrm{~s}}\right)^{2}\left(\sigma_{1 \mathrm{~s}}^{*}\right)^{2}\left(\sigma_{2 \mathrm{~s}}\right)^{2}\left(\sigma_{2 \mathrm{~s}}^{*}\right)^{2}\left(\sigma_{2 \mathrm{p}_{\mathrm{z}}}\right)^{2}$

$\left(\pi_{2 \mathrm{p}_{\mathrm{x}}}^{2}=\pi_{2 \mathrm{p}_{\mathrm{y}}}^{2}\right)\left(\pi_{2 \mathrm{p}_{\mathrm{x}}}^{*_{2}}=\pi_{2 \mathrm{p}_{\mathrm{y}}}^{*_{1}}\right)$

$\text { Bond order }=\frac{10-7}{2}=1.5$

and paramagnetic