Arrange $S$,$O$,and $Se$ in ascending order of electron affinity.

The absolute value of the electron gain enthalpy of halogens satisfies which of the following orders?

Which of the following pairs of elements would have a more negative electron gain enthalpy?
$(i)$ $O$ or $F$
$(ii)$ $F$ or $Cl$

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

The electron affinities of halogens are $F = 322$,$Cl = 349$,$Br = 324$,$I = 295 \ kJ \ mol^{-1}$. The higher value for $Cl$ as compared to that of $F$ is due to

Which of the following transformations requires the least amount of energy?