In the following the correct bond order sequence is:

$\mathrm{O}_{2}$ (16 electrons)

$\sigma_{1 \mathrm{~s}}^{2}, \sigma_{1 \mathrm{~s}}^{* 2}, \sigma_{2 \mathrm{~s}}^{2}, \sigma_{2 \mathrm{~s}}^{* 2}, \sigma_{2 p_{\mathrm{z}}}^{2}$

$\pi_{2 p_{x}}^{2}=\pi_{2 p_{y}}^{2}, \pi_{2 p_{x}}^{*_{1}}=\pi_{2 p_{y}}^{*_{1}}, \sigma_{2 p_{z}}^{*}$

Bond order of $\mathrm{O}_{2} \Rightarrow 2$

Bond order of $\mathrm{O}_{2}^{-} \Rightarrow 1.5$

Bond order of $\mathrm{O}_{2}^{2-} \Rightarrow 1$

Bond order of $\mathrm{O}_{2}^{+} \Rightarrow 2.5$