Two basic assumptions of the simple potential model applied to the carbon is electron binding energies and mean dipole moment derivatives of the fluoro-, chloro- and chlorofluoromethanes are examined. Although the relaxation energies of the fluoromethanes vary less than the experimental errors in the binding energy measurements, this is not true for the chloro- and chlorofluoromethanes Correction of the potential model for the relaxation effects results in a statistically significant improvement in the potential model regression results. A charge-charge flux-overlap model analysis using nb initio results of MP2/6-311++G(3d,3p) wave function calculations shows that the total mean dipole moment derivatives are essentially equivalent to their charge contributions for the atoms in the fluoromethanes. This indicates that the mean dipole moment derivatives can be interpreted as atomic charges for these molecules. On the other hand, charge flux and overlap contributions are very important for the chloro- and chlorofluoromethanes. In spite of this complication the carbon Is binding energies and mean dipole moment derivatives can be described by the simple potential model for all the chlorofluoromethanes treated here. Also this model leads to a theoretical prediction of the fundamental infrared intensity sum for CCl4 of 308.9 km.mol(-1), slightly lower than the measured value of 322.2 km.mol(-1).76497503