In this paper, we use Sanderson's geometric mean equalization principle for electronegativity (chi) to derive expressions for molecular hardness (eta) and its derivative (gamma) that are used to estimate the electronic properties of 14 molecules and bimolecular hydrogen-bonded complexes. Beyond the determination of electronic properties, it is shown that Sanderson's scheme can be very useful as a method for rationalizing chemical reactions when both N and upsilon change. We have found that the conditions of maximum hardness and minimum polarizability complement the minimum energy criterion for stability of molecular aggregates. Finally, we propose a new scheme for obtaining molecular properties from the isolated fragments that produces results that are in excellent agreement with those determined through Sanderson's scheme.