Structure of atoms and molecules: Electronic theory of valence

A digest of present theories regarding the structure of atoms and molecules is presented herewith. In an article of this length it is impossible to show adequately how bulk properties of substances are related to atomic properties; the article is intended primarily as a general introduction to the subject, and for those wishing to delve deeper into the matter a list of references is given at the end of the article. This is the sixth of a series of special articles prepared under sponsorship of the A.I.E.E. committee on education.