The correct order of electron affinity of $B, C, N, O$ is

Which of the following ions is most unlikely to exist?

The electron affinity values are negative for:
$A$. $Be \rightarrow Be^{-}$
$B$. $N \rightarrow N^{-}$
$C$. $O^{-} \rightarrow O^{2-}$
$D$. $Na \rightarrow Na^{-}$
$E$. $Al \rightarrow Al^{-}$
Choose the most appropriate answer from the options given below:

Match the following elements in List-$I$ with their respective electron gain enthalpy values in List-$II$:

List-$I$ (Element)	List-$II$ (Electron gain enthalpy in $kJ \ mol^{-1}$)
$(A)$ $F$	$(I)$ $-141$
$(B)$ $Cl$	$(II)$ $-328$
$(C)$ $O$	$(III)$ $-200$
$(D)$ $S$	$(IV)$ $-349$

Discuss the factors affecting electron gain enthalpy and the trend in its variation in the periodic table.

The electron gain enthalpy $\Delta_{eg}H$ of $Cl_{(g)}$ is $-349 \ kJ \ mol^{-1}$. If the ground state energy of $Cl_{(g)}$ is $x \ kJ \ mol^{-1}$,the ground state energy (in $kJ \ mol^{-1}$) of $Cl^{-}_{(g)}$ is