In chemical thermodynamics, Gilbert Newton Lewis (1875-1946) was an American physical chemist notable for the publication of his 1923 textbook Thermodynamics and the Free Energy of Chemical Substances written with American physical chemist Merle Randall, being one of the most referenced thermodynamics publications of the 20th century. In relation to their stature in the field of chemical thermodynamics, according to American chemical thermodynamicists Bevan Ott and Juliana Boerio-Goates, referring also to the work of English physical chemist Edward Guggenheim: [2]

“Lewis, Randall and Guggenheim must be considered as the founders of modern chemical thermodynamics because of the major contributions of these two books in unifying the applications of thermodynamics to chemistry.”

Lewis, who became the head of the chemistry department at the University of California, Berkeley, stimulating thermodynamics research there, between the years 1912 and 1946, his influence, and many students, have since come to be associated with the “Lewis school of thermodynamics”.

Education
Lewis educated at home by his parents in the style of the English tutoring system. His only public schooling occurred between the ages of 9 to 14 years in Lincoln, Nebraska. At age fourteen, Lewis entered the University of Nebraska but transferred to Harvard College after three years. Lewis completed his BS (1893), his MA (1898), and PhD (1899) at Harvard. His thesis was “Some Electrochemical and Thermochemical Reactions of Zinc and Cadmium Amalgams”, which was published jointly with American chemist Theodore Richards. [11] Richards trained him in experimental techniques, careful measurements, and fostered his interest in thermodynamics. [3]

Lewis stayed as an instructor at Harvard for a year before taking a traveling fellowship, studying under the physical chemists Wilhelm Ostwald at Leipzig and Walther Nernst at Göttingen. [4] He later returned to work for a period at Massachusetts Institute of Technology and in 1900 to 1907 he expanded and clarified the work of American engineer Willard Gibbs’ thermodynamics and introduced and developed concepts such as fugacity and activity. [5]

Chemical bond
Aside for his work in thermodynamics, Lewis also pioneered the Lewis dot structures, of labeling electrons in paired dots around atoms, developed 1902 during his lectures at Harvard, wrote the famous 1916 article “The Atom and the Molecule”, and developed a basic theory of chemical bonding. In particular, in about 1900, Lewis began to use dots in lecture, while teaching undergraduates at Harvard, to represent the electrons around atoms. His students favored these drawings, which stimulated him in this direction. From these lectures, Lewis noted that elements with a certain number of electrons seemed to have a special stability. This phenomenon was pointed out by the German chemist Richard Abegg in 1904, to which Lewis referred to as "Abegg's law of valence" (now generally known as Abegg's rule). To Lewis it appeared that once a core of eight electrons has formed around a nucleus, the layer is filled, and a new layer is started. Lewis also noted that various ions with eight electrons also seemed to have a special stability. On these views, he proposed the rule of eight or octet rule: Ions or atoms with a filled layer of eight electrons have a special stability. [6]

Lewis cubit atoms bonding at electron corners to form chemically bonded cubit moleculesB, in such a matter that each atom finds the most atom finds the most stability when it satisfies "Abegg's law of valence" (shells filled with eight electrons are especially stable).

In other words, electron-pair bonds are formed when two atoms share an edge, as in structure C below. This results in the sharing of two electrons. Similarly, charged ionic-bonds are formed by the transfer of an electron from one cube to another, without sharing an edge A. An intermediate state B where only one corner is shared was also postulated by Lewis. Hence, double bonds are formed by sharing a face between two cubic atoms. This results in the sharing of four electrons.

Moreover, noting that a cube has eight corners Lewis envisioned an atom as having eight sides available for electrons, like the corner of a cube. Subsequently, in 1902 he devised a conception in which cubic can bond on their sides to form cubic-structured molecules. In 1913, while working as the chair of the department of chemistry at the University of California, Berkeley Lewis read a preliminary outline of paper by an English graduate student, Alfred Lauck Parson, who was visiting Berkeley for a year. In this paper, Parson suggested that the electron is not merely an electric charge but is also a small magnet (or "magneton" as he called it) and furthermore that a chemical bond results from two electrons being shared between two atoms. [7] This, according to Lewis, meant that bonding occurred when two electrons formed a shared edge between two complete cubes.

On these views, in his famous 1916 article The Atom and the Molecule, Lewis introduced the “Lewis structure” to represent atoms and molecules, where dots represent electrons and lines represent covalent bonds. [8] In this article, he developed the concept of the electron-pair bond, in which two atoms may share one to six electrons, thus forming the single electron bond, a single bond, a double bond, or a triple bond. In his own words: “An electron may form a part of the shell of two different atoms and cannot be said to belong to either one exclusively.”

Lewis proposed that an atom tended to form an ion by gaining or losing the number of electrons needed to complete a cube. Thus, Lewis structures show each atom in the structure of the molecule using its chemical symbol. Lines are drawn between atoms that are bonded to one another; occasionally, pairs of dots are used instead of lines. Excess electrons that form lone pairs are represented as pair of dots, and are placed next to the atoms on which they reside. To summarize his views on his new bonding model, Lewis stated:

“Two atoms may conform to the rule of eight, or the octet rule, not only by the transfer of electrons from one atom to another, but also by sharing one or more pairs of electrons...Two electrons thus coupled together, when lying between two atomic centers, and held jointly in the shells of the two atoms, I have considered to be the chemical bond. We thus have a concrete picture of that physical entity, that "hook and eye" which is part of the creed of the organic chemist.”

Conservation of photons
Lewis was the person who coined the word photon. In a letter titled "The Conservation of Photons", dated October 29, 1926, to the editor of Nature magazine, Lewis wrote: [10]

“I therefore take the liberty of proposing for this hypothetical new atom, which is not light but plays an essential part in every process of radiation, the name photon."

Later life

See main: Founders of thermodynamics and suicide

Lewis, who is reported to have died from a heart attack, was found dead with a bottle of very poisonous liquid hydrogen cyanide near his body.

References
1. Lewis, Gilbert N. and Randall, Merle. (1923). Thermodynamics and the Free Energy of Chemical Substances, McGraw-Hill Book Co., Inc.
2. Boerio-Goates, Juliana, and Ott, J., Bevan. (2000). Chemical Thermodynamics - Principles and Applications. Elsevier Academic Press.
3. Gilbert Newton Lewis: American Chemist (1875-1946) – Woodrow.org.
4. Edsall, J. T. (1974). "Some notes and queries on the development of bioenergetics. Notes on some "founding fathers" of physical chemistry: J. Willard Gibbs, Wilhelm Ostwald, Walther Nernst, Gilbert Newton Lewis". Mol. Cell. Biochem. Nov. 5 (1-2): 103–12.
5. Laidler, Keith J. (1993). The World of Physical Chemistry (pg. 437). Oxford University Press.
6. Cobb, Cathy (1995). Creations of Fire - Chemistry's Lively History From Alchemy to the Atomic Age. Perseus Publishing.
7. Parson, A.L. (1915). "A Magneton Theory of the Structure of the Atom". Smithsonian Publication 2371, Washington.
8. Lewis, Gilbert. (1916). “The Atom and the Molecule” (abstract), Journal of the American Chemical Society, Vol. 38, Jan. pgs. 762-86.
9. Valence and The Structure of Atoms and Molecules", G. N. Lewis, American Chemical Society Monograph Series, page 79 and 81.
10. (a) Lewis, Gilbert N. (1926). “Letter to the Editor of Nature”, Vol. 118, Part 2, December 18, page 874-875.
(b) Origin of the word “photon” – Nobeliefs.com.
11. Hildebrand, Joel H. (1947). “Gilbert Newton Lewis: 1875-1946”, Obituary Notices of the Royal Society, 5: 491-506.

Further reading
● Lewis, Gilbert N. (1946). “Terrestrial Thermodynamics of an Ice Age: the cause and Sequence of Glaciation”, Science, 104: 43-47.
● Dunlap, Knight. (1946). “Terrestrial Thermodynamics of an Ice Age”, Science, 104, pg. 20.

External links
● Gilbert Lewis – Wikipedia.
● Gilbert Lewis – Eric Weisstein’s World of Scientific Biography.