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

The electron affinity for the inert gases is

Would you expect the second electron gain enthalpy of $O$ to be positive,more negative,or less negative than the first? Justify your answer.

In which of the following cases will the maximum energy be released?

The formation of the oxide ion $O_{(g)}^{2-}$ requires first an exothermic and then an endothermic step as shown below. This is because
$O_{(g)} + e^{-} \rightarrow O_{(g)}^{-}; \Delta H^{o} = -142 \ kJ \ mol^{-1}$
$O_{(g)}^{-} + e^{-} \rightarrow O_{(g)}^{2-}; \Delta H^{o} = 844 \ kJ \ mol^{-1}$

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