TITLE:
The Genesis of the Quantum Theory of the Chemical Bond
AUTHORS:
Salvatore Esposito, Adele Naddeo
KEYWORDS:
Chemical Bond, Molecular Orbitals, Quantum Resonance, Homopolar Compounds
JOURNAL NAME:
Advances in Historical Studies,
Vol.3 No.5,
December
23,
2014
ABSTRACT: An historical overview is given of the relevant steps that allowed the genesis of the quantum
theory of the chemical bond, starting from the appearance of the new quantum mechanics and
following later developments till approximately 1931. General ideas and some important details
are discussed concerning molecular spectroscopy, as well as quantum computations for simple
molecular systems performed within perturbative and variational approaches, for which the Born-
Oppenheimer method provided a quantitative theory accounting for rotational, vibrational and
electronic states. The novel concepts introduced by the Heitler-London theory, complemented by
those underlying the method of the molecular orbitals, are critically analyzed along with some of
their relevant applications. Further improvements in the understanding of the nature of the
chemical bond are also considered, including the ideas of one-electron and three-electron bonds
introduced by Pauling, as well as the generalizations of the Heitler-London theory firstly performed
by Majorana, which allowed the presence of ionic structures into homopolar compounds and
provided the theoretical proof of the stability of the helium molecular ion. The study of intermolecular interactions, as developed by London, is finally examined.