Arrange the three halogens $Cl$,$Br$,and $I$ in the increasing order of their electron affinity. Which of the following arrangements is correct?

The electron affinity of sulfur is........

The difference between electron gain enthalpies will be maximum between:

When an electron is added to elements of group $16$ and $17$ in $n = 2$ and $n = 3$ shells,which case experiences less electron-electron repulsion and why?

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

Which of the following has the highest electron affinity $(EA)$?