Lewis-Langmuir theory

William H. Brock. The Norton History of Chemistry. New York W. W. Norton Co., 1993. Source for Lewis-Langmuir theory early plastics Staudinger controversy available technology carbon dioxide emissions, but relatively clean technology. 

Niels Bohr s 1913 hydrogen atom paper demonstrates the traditional interest of some physicists in placing the facts and laws of chemistry within a broader framework of foundational principles laid out by physicists. During the course of the next two decades, a number of physicists who became known as quantum physicists developed physical theories and mathematical techniques that they claimed would create a mathematical and theoretical chemistry. However, few of them had much chemical knowledge beyond a general understanding of the periodic table of the elements and familiarity with the Lewis-Langmuir theory of the electron duplet and octet. 

Everywhere there appears the strong tendency to the formation of complete octets as required by the Lewis-Langmuir theory (see also p. 200), owing to the relative stability of the inert gas configuration. 

Hypervalent molecules and ions are fascinating species, since they appear to violate the traditional Lewis-Langmuir theory of bonding by expanding the valence shell of a main gronp element. Althongh species snch as PCI5,... 

If hypervalent literally means exceeding the lowest chemical valence, then even NH4+ is hypervalent, despite the fact that the Lewis-Langmuir theory easily accounts for its stability. Furthermore, if the definition of hypervalency is restricted to Groups 15-18, then this artificially excludes species such as SiFs and SiFe, which are isoelectronic and isostructural with PF5 and SFe, respectively. The ambiguities in the original definition have led to several changes. Today, no one would regard NH4+ as hypervalent, while those that consider PF5 and SFe hypervalent would classify SiFs" and SiFe in the same way. 

The atomic and molecular volumes of inorganic liquids were considered from the point of view of the Lewis-Langmuir theory of atomic structure by Pease.2 Tasiro gave the formula log v=[ml /(p+k)]+log Voo, where Vao=sp. vol. at infinite pressure, iw=tangent of the angle between the isotherm and the abscissa axis, fc=an arbitrary constant 2 5651 Voo=b (van der Waals s constant). 

Lewis s shared electron-pair theory languished tmtil Langmuir revived and elaborated it beginning in 1919. It was soon accepted as the Lewis-Langmuir theory, one of the most fundamental concepts in the history of chemistry. 

The Lewis-Langmuir theory was especially convenient for organic compounds, since the bonds between one carbon atom and another or between one carbon atom and a hydrogen atom were easily explained in this fashion. Most organic molecules could therefore easily be represented by electronic formulas where, in general, the old dash of the Kekul6 formula (see page 112) was replaced by a shared electron pair. 

Robert E. Kohler, "The Lewis-Langmuir theory of valence and the chemical community, 1920-1928," Historical studies in the physical sciences, 6 2 (1975), 431-468, on 445-451. 

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