The bond length of the species ${\mathrm{O}}_2, {\mathrm{O}}_2^{+} \mathrm{and} {\mathrm{O}}_2^{-}$ are in the order of

As bond order increases bond length decrease, the bond order of species are

$$\begin{gathered} =\frac{\mathrm{Number} \mathrm{of} \mathrm{bonding} \mathrm{electron}-\mathrm{Number} \mathrm{of} \mathrm{antibonding} \mathrm{electron}}{2} \\ \mathrm{For} {\mathrm{O}}_2 = \frac{10-6}{2}=2; {\mathrm{O}}_2^{+} = \frac{10-5}{2}=2.5 \\ {\mathrm{O}}_2^{-} = \frac{10-7}{2}=1.5 \\ \mathrm{So}, \mathrm{bond} \mathrm{order} {\mathrm{O}}_2^{+} > {\mathrm{O}}_2 > {\mathrm{O}}_2^{-} \mathrm{and} \mathrm{bond} \mathrm{length} \mathrm{are} \\ {\mathrm{O}}_2^{+} > {\mathrm{O}}_2 > {\mathrm{O}}_2^{-}. \end{gathered}$$