We have investigated the relationship between two methods to obtain mean excitation energies of large samples using a modified Bragg rule, one method using Bragg’s rule to determine elemental mean excitation energies from experimental stopping power data, and another method going the opposite way, that is determining compound mean excitation energies from theoretical elemental mean excitation energies and bond correction factors. We show how to obtain bond correction factors from elemental mean excitation energies and vice versa. The comparison leads to insight into the importance of the effect of chemical binding on the experimentally determined elemental mean excitation energies. We also introduce the concept of atomic correction factor that links theoretical, gas phase atomic mean excitation energies to elemental mean excitation energies.