Choose the correct order of $\Delta H_{eg}$ ?
$(\Delta H_{eg} = \text{electron gain enthalpy})$

The formation of the oxide ion,$O^{2-}_{(g)}$ from an oxygen atom requires first an exothermic and then an endothermic step as shown below:
$O_{(g)} + e^- \to O^{-}_{(g)} ; \Delta_f H^o = -141 \ kJ \ mol^{-1}$
$O^{-}_{(g)} + e^- \to O^{2-}_{(g)} ; \Delta_f H^o = +780 \ kJ \ mol^{-1}$
Thus,the process of formation of $O^{2-}$ in the gas phase is unfavourable even though $O^{2-}$ is isoelectronic with neon. This is due to the fact that,

Which of the following statements is correct?

The electron affinity of $Be$ is similar to :-

The electron gain enthalpy values (in $kJ \ mol^{-1}$) of three halogens $X$,$Y$ and $Z$ are respectively $-349$,$-333$ and $-325$. Then $X$,$Y$ and $Z$ are respectively

The least stable ion is