The electron affinities of some of the elements of second period (i.e., etc.) are however, lower than the corresponding elements (i.e., P, S, Cl , etc.) of the third period. This is due to the reason that the elements of second period have the smallest atomic size amongst the elements in their respective groups. As a result, there are considerable electron-electron repulsion within the atom itself and hence the additional electron is not accepted with the same ease as is the case with the remaining elements in the same group.