In this letter, we applied the discrete and continuous Tsallis' entropy, defined in terms of the occupation numbers and the electron density of atoms in their basal state. Our results show that only the discrete version of this entropy in the interval 0.0 < q < 2.0 gives a consistent behavior with respect to the electron correlation effects of the systems, while the continuous expression in some cases presents negative values, and in general decreases when the correlation effects increase. (C) 2017 Elsevier B.V. All rights reserved.