where 𝑛 %&& is the number of occupied spin orbitals, and 𝜀 ! the eigenvalue associated to the 𝑖 th spin orbital. It is the quantity 𝜒̅ -when averaging only over valence electrons -that some of us and others have linked to the central concept of electronegativity and used productively to make predictions on reactivity, 31,32 chemical bonding and high-pressure phenomena. The average electron energy 𝜒̅ , can be evaluated at different levels of theory, at drastically different computational cost. One computationally attractive approximation to 𝜒̅ within Density Functional Theory (DFT), which we will extend upon herein, is to average eigenvalues of occupied Kohn Sham (KS) orbitals. In our past work on molecules, we have relied on such a KS-DFT approximation to 𝜒̅ resolved in three dimensions,