The correct order of electron gain enthalpy is

The formation of oxide ion $O^{2-}$ from oxygen atom requires an exothermic reaction,followed by an endothermic step as shown below. The process of formation of $O^{2-}$ in gas phase is unfavorable $(\Delta H^{\ominus} = +ve)$,even though it has the stable configuration of the nearest noble gas neon. This is because:
$O_{(g)} + e^{-} \longrightarrow O^{-}_{(g)} ; \Delta H^{\ominus} = -141 \ kJ \ mol^{-1}$
$O^{-}_{(g)} + e^{-} \longrightarrow O^{2-}_{(g)} ; \Delta H^{\ominus} = +760 \ kJ \ mol^{-1}$

Which of the following species has the highest electron affinity?

In which of the following processes is energy absorbed?

Which of the following will have the most negative electron gain enthalpy and which the least negative?
$P, S, Cl, F$
Explain your answer.

The electron affinity of the following elements can be arranged as: