Identify the set of elements in which they are arranged in the increasing order of electron gain enthalpies.

Electron affinity is the

The correct order of electron gain enthalpy 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).

The correct order of the electron gain enthalpy of the given elements is

Which of the following has the least electron affinity in $kJ\,mol^{-1}$?