The average $\mathrm{C}-\mathrm{C}$ bond energy is $343 \mathrm{kJ}/\mathrm{mol}$. What do you predict for the $\mathrm{Si}-\mathrm{Si}$ single-bond energy?

Select the correct statement(s).

($\mathrm{I}$) Polarizability of ${\mathrm{S}}^{2-}$ is lower than ${\mathrm{Se}}^{2-}$
($\mathrm{II}$) Polarizability of ${\mathrm{S}}^{2-}$ is higher than ${\mathrm{Cl}}^{-}$
($\mathrm{III}$) Polarizability of ${\mathrm{S}}^{2-}$ is lower than ${\mathrm{P}}^{3-}$
($\mathrm{IV}$) Polarizability of ${\mathrm{O}}^{2-}$ is higher than ${\mathrm{S}}^{2-}$