Question

fluorine is the most electronegative element while the electron gain enthalpy of chlorine is the highest. why?

Answer 1

Dear Student, Electron gain enthalpy is the enthalpy change when one electron is accepted by a neutral gaseous atom while electronegativity is the tendency of an atom to keep the bond pair closer to itself. F has highest electronegativity but not electron gain enthalpy because it is smaller in size than chlorine and the incoming electron feels repulsion by the five 2p electrons already present. This does not happens with Cl and so, Cl has highest electron gain enthalpy. Regards