Editing Gilbert N. Lewis (section)

===Valence theory===
[[Image:Lewis-cubic-notes.jpg|300px|right|thumb|Lewis' '''[[cubical atom]]s''' (as drawn in 1902)]]

About 1902 Lewis started to use unpublished drawings of [[cubical atom]]s in his lecture notes, in which the corners of the cube represented possible [[electron]] positions. Lewis later cited these notes in his classic 1916 paper on chemical bonding, as being the first expression of his ideas.

A third major interest that originated during Lewis’ Harvard years was his valence theory. In 1902, while trying to explain the laws of valence to his students, Lewis conceived the idea that atoms were built up of a concentric series of cubes with electrons at each corner. This “cubic atom” explained the cycle of eight elements in the periodic table and was in accord with the widely accepted belief that chemical bonds were formed by transfer of electrons to give each atom a complete set of eight. This electrochemical theory of valence found its most elaborate expression in the work of [[Richard Abegg]] in 1904,<ref>{{cite journal |last1=Abegg |first1=R. |title=Die Valenz und das periodische System. Versuch einer Theorie der Molekularverbindungen |journal=Zeitschrift für Anorganische Chemie |date=1904 |volume=39 |issue=1 |pages=330–380 |url=https://babel.hathitrust.org/cgi/pt?id=uc1.b3959087;view=1up;seq=344 |trans-title=Valency and the periodic table. Attempt at a theory of molecular compounds |language=de|doi=10.1002/zaac.19040390125 }}</ref> but Lewis’ version of this theory was the only one to be embodied in a concrete atomic model. Again Lewis’ theory did not interest his Harvard mentors, who, like most American chemists of that time, had no taste for such speculation. Lewis did not publish his theory of the cubic atom, but in 1916 it became an important part of his theory of the shared electron pair bond.

In 1916, he published his classic paper on chemical bonding "''The Atom and the Molecule''"<ref>{{cite journal |last1=Lewis |first1=Gilbert N. |title=The atom and the molecule |journal=Journal of the American Chemical Society |date=April 1916 |volume=38 |issue=4 |pages=762–785 |doi=10.1021/ja02261a002 |bibcode=1916JAChS..38..762L |s2cid=95865413 |url=https://babel.hathitrust.org/cgi/pt?id=hvd.hs1t2w;view=1up;seq=772}}</ref> in which he formulated the idea of what would become known as the [[covalent bond]], consisting of a [[shared pair]] of electrons, and he defined the term odd molecule (the modern term is [[free radical]]) when an electron is not shared. He included what became known as [[Lewis structure|Lewis dot structure]]s as well as the [[cubical atom]] model. These ideas on [[chemical bond]]ing were expanded upon by [[Irving Langmuir]] and became the inspiration for the studies on the nature of the chemical bond by [[Linus Pauling]].