Which of the following has minimum bond length?

${\mathrm{O}}_2(8+8=16)={\mathrm{\sigma ls}}^2,\sigma 1^{*}{s}^2,\mathrm{\sigma }2{\mathrm{s}}^2,{\mathrm{\sigma }}^{*}2{\mathrm{s}}^2,\mathrm{\sigma }2{\mathrm{p}}_{\mathrm{z}}^2$$(\mathrm{\pi }2{\mathrm{p}}_{\mathrm{x}}^2\approx \mathrm{\pi }2{\mathrm{p}}_{\mathrm{y}}^2)({\mathrm{\pi }}^{*}2{\mathrm{p}}_{\mathrm{x}}^1\approx {\mathrm{\pi }}^{*}2{\mathrm{p}}_{\mathrm{y}}^1)$

$\text{ Bond order }=\frac{10-6}{2}=2$

Similarly, ${\mathrm{O}}_2^{+}(8+8-1=15)$

$\mathrm{BO}=\frac{10-5}{2}=2.5$

$\Rightarrow {\mathrm{O}}_2^{-}(8+8+1=17),\mathrm{BO}=\frac{10-7}{2}=1.5$

$\Rightarrow {\mathrm{O}}_2^{2-}(8+8+2=18)\mathrm{BO}=\frac{10-8}{2}=1$

$\text{∴ Bond order ∝}\frac{{\displaystyle 1}}{{\displaystyle \mathrm{bondlength} }}$

Thus, ${\mathrm{O}}_2^{+}$ has the minimum bond length as its bond order is maximum.