# Why does chlorine have a higher electron affinity than fluorine?

Since fluorine has its valence electrons in the n=2 energy level, and since chlorine has its valence electrons in the n=3 energy level, one would initially expect that an electron rushing towards fluorine would release more energy, as it would land in the n=2 energy level, whereas in chlorine, the electron would land only in the n=3 energy level, and would then not release as much energy. Thus, one would expect fluorine to have a greater electron affinity than chlorine. However, why is it that chlorine has a higher electron affinity (349 kJ/mol) than fluorine (328.165 kJ/mol)?

• @user3932000 Chlorine have vacant d-orbitals. Since empty orbitals are omitted when writing electronic configuration, it is written as $1s^2 2s^2 2p^6 3s^2 3p^5$. Complete electronic configuration would be $1s^2 2s^2 2p^6 3s^2 3p^5 3d^0$. – ashu Nov 6 '16 at 14:42
• @ashu There is absolutely no reason to consider vacant d orbitals in partly filled electron shells. You don’t consider f orbitals for bromine either. In fact, while this answer does start off well I have to give it a $-1$ for invoking a concept that does not help and is introduced incorrectly. – Jan Sep 29 '17 at 8:52