Heitler and London’s hydrogen molecule paper was not, in Pauling’s view, followed up with much of value. The German pair were physicists, after all, not chemists, so they could not be expected to understand how their exchange-energy concept related to the huge cornucopia of chemical phenomena, most of which they knew nothing about. Even though they had beaten Pauling to the first successful quantum-mechanical attack on the chemical bond, there was still much he could do to expand and rework their original insight.

One of the first things he did was to prepare a long article for Chemical Reviews in which he introduced the Heitler-London chemical-bond work and added some new insights of his own into its application to the one-electron hydrogen molecule-ion. This was the first glimpse that most chemists had seen of the quantum mechanical approach to their field, and it marked Pauling’s entrance onto the American scientific stage in his new role of quantum-chemist.