In which of the following is the electron gain enthalpy of elements correctly arranged?

The electron gain enthalpy (in $kJ/mol$) of fluorine,chlorine,bromine and iodine,respectively,are:

Which of the following is correct regarding the electron affinity of halogens?

Fluorine has lower electron affinity than chlorine because of

Arrange $N$,$S$,$O$ and $F$ in order of decreasing electron gain enthalpy.

The formation of the oxide ion,$O^{2-}_{(g)}$,from oxygen atom requires first an exothermic and then an endothermic step as shown below:
$O_{(g)} + e^- \to O^{-}_{(g)} ; \Delta_f H^{\Theta} = -141 \ kJ \ mol^{-1}$
$O^{-}_{(g)} + e^- \to O^{2-}_{(g)} ; \Delta_f H^{\Theta} = +780 \ kJ \ mol^{-1}$
Thus,the process of formation of $O^{2-}$ in gas phase is unfavourable even though $O^{2-}$ is isoelectronic with neon. It is due to the fact that,