Why electron affinity of fluorine is less than that of chlorine?
E.A of fluorine is less than that of chlorine due to two reasons:
(1) Small size fluorine atom makes the 2p subshell more compact. This results in repulsion among electrons of the valence shell and also with electron to be added. Due to this F atom has less tendency to accept electron.
(2) Because of small size of fluorine, there will be high electron density around the nucleus. This high electron density screens the nucleus. Because of this, effective nuclear charge gets decreased. Thus, the electron is having less attraction during addition. Hence, electron affinity of fluorine gets decreased.