The correct order of electron gain enthalpy of $N$,$O$,$Cl$,$Al$ is

Knowing the electron gain enthalpy values for $O \rightarrow O^{-}$ and $O \rightarrow O^{2-}$ as $-141 \ kJ \ mol^{-1}$ and $702 \ kJ \ mol^{-1}$ respectively,how can you account for the formation of a large number of oxides having $O^{2-}$ species and not $O^{-}$?
(Hint: Consider lattice energy factor in the formation of compounds).

In comparison with alkali metals,the electron affinity of halogens is

In which of the following processes is energy absorbed?

Which of the following has the highest electron affinity?

Which electron affinity process would liberate the most energy?