The electron affinities of halogens are generally very high, but the value for Fluorine is unexpecte — Periodic Table and Periodicity Chemistry Question

💡 Solution & Explanation

Fluorine has an exceptionally small atomic size. The incoming electron must enter the very compact $2p$ subshell, which already houses 5 electrons. This causes massive inter-electronic repulsion, counteracting the nuclear attraction and resulting in less energy release compared to Chlorine's larger $3p$ subshell.