Equation describes energy changes in any chemical process. For example, when integrated over a chemical reaction eq. ( ) allows the study of how individual atomic energy contributions evolve. We focus on the conceptual meaning of the first right-hand side term of eq. ( ) in what follows but remind that the second term relates to chemical hardness. The quantification of all these terms is possible through different methods (e.g., see Ref. 133) and we will return to discuss their physical rationale and implications in detail, in future work.