Electronegativity equalization: taming an old problem with new tools

Electronegativity equalization is examined after understanding an atom-in-a-molecule as an open quantum system, characterized by a variable fluctuating number of electrons whose average is set through charge-constrained electronic structure calculations. It is shown that actual results in toy systems can be easily modeled through electron distribution functions, and that by doing so several conflicting interpretations converge onto a common formalism.