The set containing the elements with positive electron gain enthalpies is

The order of negative electron gain enthalpy of $Li$,$Na$,$S$,$Cl$ is

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 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:
$O_{(g)} + e^{-} \longrightarrow O^{-}_{(g)} ; \Delta H^{\ominus} = -141 \ kJ \ mol^{-1}$
$O^{-}_{(g)} + e^{-} \longrightarrow O^{2-}_{(g)} ; \Delta H^{\ominus} = +760 \ kJ \ mol^{-1}$

Electron affinity depends on

The correct order of increasing electron affinity of the following elements is