Ans: (B, C)
: \(\mathrm{O}_{2}^{2-}\) is the peroxide ion:
$$
\mathrm{O}_{2}^{2-}:\left(\sigma_{1 \mathrm{~s}}^{\mathrm{b}}\right)^{2}\left(\sigma_{1 \mathrm{~s}}^{*}\right)^{2}\left(\sigma_{2 \mathrm{~s}}^{\mathrm{b}}\right)^{2}\left(\sigma_{2 \mathrm{~s}}^{*}\right)^{2}\left(\sigma_{z}^{\mathrm{b}}\right)^{2}\left(\pi_{\mathrm{x}}^{\mathrm{b}}\right)^{2}=\left(\pi_{\mathrm{y}}^{\mathrm{b}}\right)^{2}\left(\pi_{\mathrm{x}}^{*}\right)^{2}=\left(\pi_{\mathrm{y}}^{*}\right)^{2}
$$
No unpaired electron implies it is diamagnetic in nature:
Bond order \(=\frac{10-8}{2}=1\)
