(a) Halogens have maximum negative gain enthalpy in the respective periods of the periodic table. Why?
(b) Although electron gain enthalpy of fluorine is less negative as compared to chlorine, fluorine is a stronger oxidising agent than chlorine . Why?
Fluorine exhibits only-1 oxidation state, whereas other halogens exhibit `+1,+3,+5, and +7` oxidation states also. Explain.

Explanation

It is due to.
(i) low enthalpy of dissociation of F-F bond (Table 7.8).
(ii) high hydration enthalpy of `F^(–)` (Table 7.8).