and Eq.17, respectively. Eventually, the BEBOP model generates the individual σ and π molecular bond energy components as elements from lower-diagonal matrices. The C-H diatomic molecule nicely illustrates the significance of each energy component (Figure ). The We can rescale the BEBOP net bond energies to reproduce the ROCBS-QB3 energies exactly (Figure ), but the agreement is sufficiently good before rescaling that our interpretation remains unchanged. Bond energies and charges of atoms in molecules are useful intuitive concepts that have enjoyed wide acceptance as qualitative parameters, but cannot be given unique quantitative definitions. Just as the only rigorous constraint on "atomic charges" is that the sum of these charges equal the total charge of the molecule, the only rigorous constraint on bond energies is that the sum of the bond energies equal the total energy required to dissociate the molecule into the constituent atoms (i.e., the atomization energy).