Why is the electron gain enthalpy of oxygen or fluorine are less than that of sulphur or chlorine?

In which of the following pairs, electron gain enthalpies of constituent elements are nearly the same or identical?

(A) $\mathrm{Rb}$ and $\mathrm{Cs}$

(B) $\mathrm{Na}$ and $\mathrm{K}$

(C) $\mathrm{Ar}$ and $\mathrm{Kr}$

(D) $\mathrm{I}$ and $\mathrm{At}$

Choose the correct answer from the options given below:

The difference between electron gain enthalpies will be maximum between :

What is the correct oder of electron gain enthalpy of $\mathrm{Cl}, \mathrm{F}, \mathrm{Te}, \mathrm{Po}$

Which of the following reactions does not involve absorption of energy?

I. $\mathrm{O}\left(\mathrm{g}\right)+{\mathrm{e}}^{-}⟶{\mathrm{O}}^{-}\left(\mathrm{g}\right)$

II. $\mathrm{S}\left(\mathrm{g}\right)+{\mathrm{e}}^{-}⟶{\mathrm{S}}^{-}\left(\mathrm{g}\right)$

III. ${\mathrm{O}}^{-}\left(\mathrm{g}\right)+{\mathrm{e}}^{-}⟶{\mathrm{O}}^{2-}\left(\mathrm{g}\right)$

IV. $\mathrm{Cl}\left(\mathrm{g}\right)+{\mathrm{e}}^{-}⟶{\mathrm{Cl}}^{-}\left(\mathrm{g}\right)$

Match the following :

Arrange the following according to the instruction given in bracket:

$\mathrm{F}, \mathrm{B}, \mathrm{N}, \mathrm{O}$ (In the increasing order of electron affinity)