We report a detailed characterization of the valence shell charge concentration (VSCC) of fluorine in methyl fluoride through the atoms in molecules theory. A comparison between the VSCCs of fluorine and neighboring elements (N, O, P, S, Cl) in the periodic table is also presented. The fluorine VSCC is shown to be tetrahedral and the most compact with the highest values of rho and -del(2)rho. Our results calculated at several post Hartree-Fock levels of theory using a large basis set show a remarkable insensitivity to the level of theory. (C) 2004 Elsevier B.V. All rights reserved.