where 0(r) is the reference electron density satisfying the same normalization condition as (r). The first example of applying ITA quantities to appreciate electronic properties was by Nalewajski and Parr, who showed that minimizing Eq. ( ) subject to the normalization condition of the electron density results in the Hirshfeld partition of atoms in molecules. We also have devoted much effort in the past few years to developing a reactivity framework in terms of ITA quantities and applied to quantify, e.g., acidity and aromaticity. ■