 A second challenge to the structural conception of bonding comes from computational chemistry, the application of quantum mechanics to make predictions about chemical phenomena. Drawing on the work of quantum chemist Charles Coulson (1910–1974), Weisberg (2008) has argued that the structural conception of chemical bonding is not robust in quantum chemistry. This argument looks to the history of quantum mechanical models of molecular structure. In the earliest quantum mechanical models, something very much like the structural conception of bonding was preserved; electron density was, for the most part, localized between atomic centers and was responsible for holding molecules together. However, these early models made empirical predictions about bond energies and bond lengths that were only in qualitative accord with experiment.