Question

Electron Affinity of Cl > F, why?

Answer 1

Fluorine, though higher than chlorine in the periodic table, has a very small atomic size. This makes the fluoride anion so formed unstable (highly reactive) due to a very high charge/mass ratio. As a result, fluorine has an electron affinity less than that of chlorine.

Answer 2

chlorine has greater size than fluorine and due to their the repulsion between them is less so electron affinity of chlorine is greater than fluorine