The electron affinity of chlorine is $3.7 \ eV$. $1 \ g$ of chlorine is completely converted to $Cl^-$ ion in a gaseous state. $(1 \ eV = 23.06 \ kcal \ mol^{-1})$. Energy released in the process is $...... \ kcal$.

The increasing order of electron affinity for the given electronic configurations of elements is:
$I. 1s^2 2s^2 2p^6 3s^2 3p^5$
$II. 1s^2 2s^2 2p^3$
$III. 1s^2 2s^2 2p^5$
$IV. 1s^2 2s^2 2p^6 3s^1$

Knowing the electron gain enthalpy values for $O \rightarrow O^{-}$ and $O \rightarrow O^{2-}$ as $-141 \ kJ \ mol^{-1}$ and $702 \ kJ \ mol^{-1}$ respectively,how can you account for the formation of a large number of oxides having $O^{2-}$ species and not $O^{-}$?
(Hint: Consider lattice energy factor in the formation of compounds).

The $CORRECT$ order of $\Delta H_{eg}$ of the following elements is

In which of the following,elements are arranged in the correct order of their electron gain enthalpies?

Within each pair of elements of $F$ and $Cl$,$S$ and $Se$,and $Li$ and $Na$,respectively,the elements that release more energy upon an electron gain are