Why electron gain enthalpy of fluorine is less than chlorine?

This is a classic chemistry question with several contributing factors:1. Small atomic size: Fluorine has a very small atomic radius, so when an extra electron is added, it experiences significant electron-electron repulsion from the existing electrons in the compact 2p orbital.2. High electron density: The small size means the electron density is already high in fluorine's valence shell, making it reluctant to accept another electron.3. Less effective shielding: In fluorine, the 2p electrons are less effectively shielded by the inner electrons compared to chlorine's 3p electrons which are better shielded by more inner shells.Despite fluorine's higher electronegativity, these factors make the actual energy released when gaining an electron (electron gain enthalpy) less negative for fluorine (-328 kJ/mol) than for chlorine (-349 kJ/mol). Chlorine's larger size allows the added electron to be accommodated with less repulsion, making the process more energetically favorable.