Gilbert Newton Lewis's memorandum of 1902 showing his speculations about the role of electrons in atomic structure. From Valence and the Structure of Atoms and Molecules (1923), p. 29.
Chemical Heritage Foundation Collections.
Gilbert Newton Lewis using a slide rule at his desk.
Once physicists studying the structure of the atom began to realize that the electrons surrounding the nucleus had a special arrangement, chemists began to investigate how these theories corresponded to the known chemistry of the elements and their bonding abilities. Two Americans who were instrumental in developing a bonding theory based on the number of electrons in the outermost "valence" shell of the atom were Gilbert Newton Lewis (1875–1946) and Irving Langmuir (1881–1957).
In 1902, while Lewis was trying to explain valence to his students, he depicted atoms as constructed of a concentric series of cubes with electrons at each corner. This "cubic atom" explained the eight groups in the periodic table and represented his theory that chemical bonds are formed by electron transference to give each atom a complete set of eight. In 1923 he redefined acids as any atom or molecule with an incomplete "octet" that were thus capable of accepting electrons from another atom; bases were, of course, electron donors.
Gilbert Newton Lewis.
Courtesy The Chemists' Club.
Lewis was also important in developing the field of thermodynamics and applying its laws to real chemical systems. At the end of the 19th century when he started working, the law of conservation of energy and other thermodynamic relations were known only as isolated equations. Lewis built on the work of another American pioneer in thermodynamics, Josiah Willard Gibbs (1839–1903) of Yale University, whose contributions were only slowly recognized. Their work was of immense value in predicting whether reactions will go almost to completion, reach an equilibrium, or proceed almost not at all, and whether a mixture of chemicals can be separated by distillation.
Irving Langmuir at home enjoying Harper's Magazine.
Irving Langmuir Scrapbook, Chemical Heritage Foundation Collections.
As a research pioneer for the General Electric Company, Irving Langmuir made scientific contributions in chemistry, physics, and atmospheric science. He received his doctorate from Walther Nernst in Göttingen, Germany, but became bored after one year of teaching college. In 1909 he arrived at the recently established GE Research Laboratory. His first job was to solve the problems they were having with the new tungsten filament light bulbs. Langmuir concentrated on the basic principles on which the lamp operated, investigating the chemical reactions catalyzed by the hot tungsten filament. He suggested filling the bulbs with nitrogen gas (and later argon gas) and twisting the filament into a spiral form to inhibit the vaporization of tungsten.
Irving Langmuir (left) with radio pioneer Guglielmo Marconi in the General Electric Research Laboratory in Schenectady, New York, in 1922.
Courtesy Edgar Fahs Smith Memorial Collection, Department of Special Collections, University of Pennsylvania Library.
His interest in fundamentals involved him in the theory of chemical bonding in terms of electrons, and he elaborated on ideas first expressed by Gilbert Lewis. Langmuir proposed that octets could be filled by sharing pairs between two atoms—the "covalent" bond. His studies of surface chemistry—the study of chemical forces at the contact surfaces (interfaces) between different substances, where so many biologically and technologically important reactions occur—earned him the Nobel Prize in chemistry in 1932. Langmuir developed a new concept of adsorption, according to which every molecule striking a surface remains in contact with it before evaporating, thus forming a firmly held monolayer—in contrast to earlier theories that likened adsorption to the attraction of the earth for the gases in the atmosphere, where the attraction diminishes as distance from the earth increases. He developed a multitude of experimental techniques, including the extensive use of vacuum tubes to study solid–gas interfaces and of oil films to study liquid–liquid interfaces. Other practical work with theoretical implications—on electrical discharges in gases—helped to lay the foundation for "plasma" physics, which has application today in attempts at controlled nuclear fusion. He maintained a lifelong interest in meteorology, including work developing aircraft de-icing capabilities during World War II. Here too Langmuir pushed beyond observation to theory, which led to his carrying out early experiments in "seeding" clouds with solid carbon dioxide particles to produce rain.