That observation, in turn, is a direct result of CT energies that are systematically larger at the interface for precisely those four surface-active anions. Statistical distributions of E CT for all of the ions are plotted in Fig. ). In contrast to other energy components, only for E CT do we observe pronounced difference between averages computed for the bulk and interfacial data sets. That said, the overall scale of the CT energies is a rather small part of either the total induction energy or the total interaction energy, with |E CT | 10 kcal/mol except in the case of interfacial ClO -. (Although CT energies smaller than 10 kcal/mol do play a pivotal role in establishing the directionality of hydrogen bonds , that kind of detailed analysis of a potential energy surface is not attempted in the present work, where we are interested in ensemble-averaged properties.) For Br -, I -, ClO - 4 , and SCN -, the average CT energy at the air/water interface is larger than its mean value in bulk water by at least one standard deviation in the bulk value. For Cl -(aq), the interfacial average value of E CT is larger in magnitude than the bulk value, though not quite by a full standard deviation. It is perhaps noteworthy that outliers for the CT energies tend to be larger at the interface, particularly towards negative (more stabilizing) values of E CT .