The correct order of electron affinity is:

The electron affinity values (in $kJ \ mol^{-1}$) for halogens $X, Y,$ and $Z$ are $-349, -333,$ and $-325$ respectively. Therefore,$X, Y,$ and $Z$ are respectively which of the following?

Which of the following represents the correct order of increasing electron gain enthalpy with negative sign for the elements $O$,$S$,$F$ and $Cl$?

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,

Which of the following represents an exothermic reaction?

Which group elements easily accept $1$ and $2$ electrons to achieve noble gas electronic configurations? Why?