Which one of the following species will have maximum bond dissociation energy?

${\mathrm{C}}_2$  (8 electrons); $\mathrm{KK}\left(\sigma 2\mathrm{s}{)}^2\right(\sigma \ast 2\mathrm{s}{)}^2{\left(\pi \ast 2{\mathrm{p}}_x\right)}^2{\left(\pi 2{\mathrm{p}}_y\right)}^2$ Bond order $=(6-2)/2=2$

${\mathrm{C}}_2^{+}$ (7 electrons);  Bond order $=(5-2)/2=11/2$

${\mathrm{C}}_2^{-}$ (9 electrons);  $\mathrm{KK}\left(\sigma 2\mathrm{s}{)}^2\right(\sigma \ast 2\mathrm{s}{)}^2{\left(\pi 2{\mathrm{p}}_x\right)}^2{\left(\pi 2{\mathrm{p}}_y\right)}^2{\left(\sigma 2{\mathrm{p}}_y\right)}^1$ Bond order $=(7-2)/2=2\frac{1}{2}$

${\mathrm{C}}_2^{2-}$ -(10 electrons);   Bond order $=(8-2)/2=3$

Larger the bond order, larger the dissociation energy.