アービング・ラングミュア(1881 – 1957) は、ルイスの電子構造理論をさらに掘り下げた論文を1919年に発表した。「THE ARRANGEMENT OF ELECTRONS IN ATOMS AND MOLECULES」がその論文だ。 ラングミュアは、その冒頭で化学と物理の現状と役目を見事に語っている。周期表にさらに精密な構造を付け加えた。
The problem of the structure of atoms has been attcked mainly by physicists who have given little consideration to the chemical properties which must ultimately be explained by a theory of atomic structure. The vast story of knowledge of chemical properties and relationships, such as is summarized by the Periodic Table, should serve as a better foundation for a theory of atomic structure than the relatively meager experimental data along purely physical lines.