Editing Gilbert N. Lewis

{{Short description|American physical chemist (1875–1946)}}
{{Use mdy dates|date=February 2024}} {{Use American English|date=February 2024}}
{{Infobox scientist
| image             = Gilbert N Lewis.jpg
| image_size        =
| caption           = 
| birth_date        = {{birth date|1875|10|23}} or {{birth date|1875|10|25}}
| birth_place       = [[Weymouth, Massachusetts]], US
| death_date        = {{death date and age|1946|03|23|1875|10|23}}
| death_place       = [[Berkeley, California]], US
| residence         = 
| citizenship       = 
| ethnicity         = 
| field             = [[physical chemistry|Physical chemist]]
| work_institutions = 
| alma_mater        = 
| thesis_title      = A general equation for free energy and physico-chemical equilibrium, and its application
| thesis_year       = 1899
| doctoral_advisor  = [[Theodore William Richards]]
| doctoral_students = [[Michael Kasha]]<br/>[[Harold Urey]]<br/>[[Glenn T. Seaborg]]<br/>[[Joseph Edward Mayer]]
| known_for         = [[Electron pair|Lewis pair]]<br/>[[Lewis structures]]<br/>[[Lewis acids and bases]]<br/>[[Trouton–Noble experiment#Right-angle lever paradox|Lewis–Tolman paradox]]<br/>[[Chemical thermodynamics]]<br/>[[Valence bond theory]]<br/>[[Covalent bond]]<br/>[[Cubical atom]]<br/>[[Fugacity]]<br/>[[Heavy water]]<br/>[[Ionic strength]]<br>[[Octet rule]]<br/>[[Tetraoxygen]]<br/>[[Thermodynamic activity]]<br/>Named [[photon]]<br/>Explained [[phosphorescence]]
| author_abbrev_bot = 
| author_abbrev_zoo = 
| prizes            = [[Fellow of the Royal Society]]<ref name="frs"/><br>[[William H. Nichols Medal]] <small>(1921)</small><br> [[Willard Gibbs Award]] <small>(1924)</small><br>[[Davy Medal]] {{small|(1929)}}
| religion          = 
| footnotes         = 
| signature         =  
}}
'''Gilbert Newton Lewis''' {{post-nominals|post-noms=[[Foreign Member of the Royal Society|ForMemRS]]}}<ref name="frs">{{Cite journal | last1 = Hildebrand | first1 = J. H. | title = Gilbert Newton Lewis. 1875-1946 | doi = 10.1098/rsbm.1947.0014 | journal = [[Obituary Notices of Fellows of the Royal Society]] | volume = 5 | issue = 15 | pages = 491–506 | year = 1947 | doi-access = free }}</ref> (October 23<ref>{{cite encyclopedia|url = https://www.britannica.com/biography/Gilbert-N-Lewis |date = 19 March 2021|title = Gilbert N. Lewis, American chemist |first = William B.|last = Jensen|author1-link=William B. Jensen |encyclopedia = Encyclopedia Britannica}}</ref><ref name=":3"/><ref name=Heritage/> or October 25, 1875 – March 23, 1946)<ref name="frs"/><ref>[http://www.nasonline.org/publications/biographical-memoirs/memoir-pdfs/lewis-gilbert-n.pdf GILBERT NEWTON LEWIS 1875—1946 A Biographical Memoir] by [[Joel H. Hildebrand]] National Academy of Sciences 1958</ref><ref>[http://www.encyclopedia.com/people/science-and-technology/chemistry-biographies/gilbert-newton-lewis Lewis, Gilbert Newton] R. E. Kohler in Complete Dictionary of Scientific Biography (Encyclopedia.com)</ref> was an American [[physical chemistry|physical chemist]] and a  dean of the college of chemistry at [[University of California, Berkeley]].<ref name=":3">{{Cite web|url=http://texts.cdlib.org/view?docId=hb300004ss;NAAN=13030&doc.view=frames&chunk.id=div00006&toc.depth=1&toc.id=&brand=calisphere|title=University of California: In Memoriam, 1946|website=texts.cdlib.org|access-date=2019-03-09}}</ref><ref name=":2">{{Cite web|url=https://www.acs.org/content/acs/en/education/whatischemistry/landmarks/gilman.html|title=Gilman Hall University of California, Berkeley - National Historic Chemical Landmark |work=American Chemical Society|language=en|access-date=2019-03-09}}</ref> Lewis was best known for his discovery of the [[covalent bond]] and his concept of [[electron pair]]s; his [[Lewis structure|Lewis dot structures]] and other contributions to [[valence bond theory]] have shaped modern theories of [[chemical bond]]ing. Lewis successfully contributed to [[chemical thermodynamics]], [[photochemistry]], and [[isotope separation]], and is also known for [[Lewis acids and bases|his concept of acids and bases]].<ref>{{Cite journal| doi = 10.1038/nchem.149 | issn = 1755-4330| volume = 1| issue = 1| pages = 19| last = Davey| first = Stephen| date = 2009| title = The legacy of Lewis| journal = Nature Chemistry| bibcode = 2009NatCh...1...19D| doi-access = free}}</ref> Lewis also researched on [[Theory of relativity|relativity]] and [[Quantum Physics|quantum physics]], and in 1926 he coined the term "[[photon]]" for the smallest unit of radiant energy.<ref>{{Cite web |url=https://www.aps.org/publications/apsnews/201212/physicshistory.cfm|date=December 2012|title=December 18, 1926: Gilbert Lewis coins "photon" in letter to Nature|publisher=American Physical Society|website=APS News: This Month in Physics History|language=en|access-date=2019-08-04}}</ref><ref name=":9" />

G. N. Lewis was born in 1875 in [[Weymouth, Massachusetts]]. After receiving his [[Doctor of Philosophy|PhD]] in [[chemistry]] from [[Harvard University]] and studying abroad in Germany and the [[Philippines]], Lewis moved to [[California]] in 1912 to teach chemistry at the University of California, Berkeley, where he became the dean of the college of chemistry and spent the rest of his life.<ref name=":3" /><ref name=":4" /> As a professor, he incorporated thermodynamic principles into the chemistry curriculum and reformed [[chemical thermodynamics]] in a mathematically rigorous manner accessible to ordinary chemists. He began measuring the [[Thermodynamic free energy|free energy]] values related to several chemical processes, both organic and inorganic. In 1916, he also proposed his theory of bonding and added information about electrons in the [[periodic table]] of the [[chemical element]]s. In 1933, he started his research on isotope separation. Lewis worked with hydrogen and managed to purify a sample of [[heavy water]]. He then came up with his theory of acids and bases, and did work in [[photochemistry]] during the last years of his life.

Though he was nominated 41 times, G. N. Lewis never won the [[Nobel Prize in Chemistry]], resulting in a major [[Nobel Prize controversies|Nobel Prize controversy]].<ref name="NobelPrize">{{cite web|url=https://www.nobelprize.org/nomination/archive/show_people.php?id=5441|title=Nomination Database Gilbert N. Lewis|website=NobelPrize.org|access-date=10 May 2016}}</ref><ref name=Heritage>{{Cite web|url=https://www.atomicheritage.org/profile/gilbert-n-lewis|title=Gilbert N. Lewis|website=Atomic Heritage Foundation|language=en|access-date=2019-03-09}}</ref><ref name=":5">{{Cite web|url=https://www.sfgate.com/bayarea/article/WHAT-KILLED-FAMED-CAL-CHEMIST-20th-century-2491757.php|title=WHAT KILLED FAMED CAL CHEMIST? / 20th century pioneer who failed to win a Nobel Prize may have succumbed to a broken heart, one admirer theorizes|last1=DelVecchio|first1=Rick|last2=Writer|first2=Chronicle Staff|date=2006-08-05|website=SFGate|access-date=2019-03-09}}</ref><ref name=":0">{{Cite web|url=https://www.aps.org/publications/apsnews/201212/physicshistory.cfm|title=December 18, 1926: Gilbert Lewis coins "photon" in letter to Nature|website=www.aps.org|language=en|access-date=2019-03-09}}</ref><ref>{{Cite journal|publisher=American Chemical Society|website=ACS Symposium Series|last=Jensen|first=William B.|title=The Mystery of G. N. Lewis's Missing Nobel Prize. The Posthumous Nobel Prize in Chemistry. Volume 1. Correcting the Errors and Oversights of the Nobel Prize Committee|date=5 October 2017|pages=107–120|doi=10.1021/bk-2017-1262.ch006}}</ref> On the other hand, Lewis mentored and influenced numerous Nobel laureates at Berkeley including [[Harold Urey]] (1934 Nobel Prize), [[William F. Giauque]] (1949 Nobel Prize), [[Glenn T. Seaborg]] (1951 Nobel Prize), [[Willard Libby]] (1960 Nobel Prize), [[Melvin Calvin]] (1961 Nobel Prize) and so on, turning Berkeley into one of the world's most prestigious centers for chemistry.<ref name=":1" /><ref name=":6" /><ref name=":7" /><ref name=":8" /><ref>{{Cite journal|last=Harris|first=Reviewed By Harold H.|date=1999-11-01|title=A Biography of Distinguished Scientist Gilbert Newton Lewis (by Edward S. Lewis)|journal=Journal of Chemical Education|volume=76|issue=11|pages=1487|doi=10.1021/ed076p1487|issn=0021-9584|bibcode=1999JChEd..76.1487H|doi-access=free}}</ref>  On March 23, 1946, Lewis was found dead in his Berkeley laboratory where he had been working with [[hydrogen cyanide]]; many postulated that the cause of his death was suicide.<ref name=":5" /> After Lewis' death, his children followed their father's career in chemistry, and the Lewis Hall on the Berkeley campus is named after him.<ref name=":4" />

==Biography==

===Early life===
Lewis was born in 1875 and raised in [[Weymouth, Massachusetts]], where there exists a street named for him, G.N. Lewis Way, off Summer Street.  Additionally, the wing of the new Weymouth High School Chemistry department has been named in his honor. Lewis received his primary education at home from his parents, Frank Wesley Lewis, a lawyer of independent character, and Mary Burr White Lewis. He read at age three and was intellectually precocious. In 1884 his family moved to [[Lincoln, Nebraska]], and in 1889 he received his first formal education at the university preparatory school.

In 1893, after two years at the [[University of Nebraska]], Lewis transferred to [[Harvard University]], where he obtained his [[B.S.]] in 1896. After a year of teaching at [[Phillips Academy]] in [[Andover, Massachusetts|Andover]], Lewis returned to Harvard to study with the physical chemist [[Theodore William Richards|T. W. Richards]] and obtained his Ph.D. in 1899 with a dissertation on [[electrochemical potential]]s.<ref>{{cite book |last1=Hildebrand |first1=Joel H. |title=Biographical Memoirs of the National Academy of Sciences |date=1958 |publisher=National Academy of Sciences |location=Washington, D.C., U.S.A. |volume= 31 |pages=209–235 |chapter=Gilbert Newton Lewis |chapter-url=http://www.nasonline.org/publications/biographical-memoirs/memoir-pdfs/lewis-gilbert-n.pdf}}; see p. 210. Lewis's Ph.D. thesis was titled "Some electrochemical and thermochemical relations of zinc and cadmium amalgams". He published the results jointly with his supervisor T.W. Richards.</ref><ref>{{cite journal |last1=Richards |first1=Theodore William |last2=Lewis |first2=Gilbert Newton |title=Some electrochemical and thermochemical relations of zinc and cadmium amalgams |journal=Proceedings of the American Academy of Arts and Sciences |date=1898 |volume=34 |issue=4 |pages=87–99 |url=https://babel.hathitrust.org/cgi/pt?id=njp.32101050586039;view=1up;seq=97|doi=10.2307/20020864 |jstor=20020864 |url-access=subscription }}</ref> After a year of teaching at Harvard, Lewis took a traveling fellowship to Germany, the center of [[physical chemistry]], and studied with [[Walther Nernst]] at [[Göttingen]] and with [[Wilhelm Ostwald]] at [[Leipzig]].<ref>{{cite journal
|last=Edsall
|first=J. T.
|date=November 1974
|title=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
|journal=[[Mol. Cell. Biochem.]]
|volume=5 |issue=1–2 |pages=103–12
|doi=10.1007/BF01874179
|pmid = 4610355
|s2cid=5682498
}}
</ref> While working in Nernst's lab, Lewis apparently developed a lifelong enmity with Nernst. In the following years, Lewis started to criticize and denounce his former teacher on many occasions, calling Nernst's work on his heat theorem "''a regrettable episode in the history of chemistry''".<ref>[http://listverse.com/2015/04/07/10-fierce-but-productive-rivalries-between-dueling-scientists/ ''10 Fierce (But Productive) Rivalries Between Dueling Scientists''] Radu Alexander. Website of Listverse Ltd. April 7th 2015. Retrieved 2016-03-24.</ref> A [[Sweden|Swedish]] friend of Nernst's, [[:sv:Wilhelm Palmær (kemist)|Wilhelm Palmær]], was a member of the Nobel Chemistry Committee. There is evidence that he used the Nobel nominating and reporting procedures to block a [[Nobel Prize]] for Lewis in [[thermodynamics]] by nominating Lewis for the prize three times, and then using his position as a committee member to write negative reports.<ref>Coffey (2008): 195-207.</ref>

===Harvard, Manila, and MIT===
After his stay in Nernst's lab, Lewis returned to Harvard in 1901 as an instructor for three more years. He was appointed instructor in [[thermodynamics]] and [[electrochemistry]]. In 1904 Lewis was granted a leave of absence and became Superintendent of Weights and Measures for the Bureau of Science in [[Manila]], [[Philippines]]. The next year he returned to [[Cambridge, Massachusetts]] when the [[Massachusetts Institute of Technology]] (MIT) appointed him to a faculty position, in which he had a chance to join a group of outstanding physical chemists under the direction of [[Arthur Amos Noyes]]. He became an assistant professor in 1907, associate professor in 1908, and full professor in 1911.

===University of California, Berkeley===
G. N. Lewis left MIT in 1912 to become a professor of physical chemistry and dean of the [[Berkeley College of Chemistry|College of Chemistry]] at the [[University of California, Berkeley]].<ref name=":0" /><ref name=":1">{{Cite web|url=https://www.acs.org/content/acs/en/education/whatischemistry/landmarks/gilman.html|title=Gilman Hall University of California, Berkeley - National Historic Chemical Landmark|website=American Chemical Society|language=en|access-date=2019-03-09}}</ref> On June 21, 1912, he married Mary Hinckley Sheldon, daughter of a Harvard professor of [[Romance languages]]. They had two sons, both of whom became chemistry professors, and a daughter. In 1913, he joined the [[Alpha Chi Sigma]] at Berkeley, the professional chemistry fraternity.<ref>{{Cite web|url=https://axs.berkeley.edu/about.html|title=About - Alpha Chi Sigma {{!}} Sigma Chapter|website=axs.berkeley.edu|access-date=2019-03-09|archive-date=July 29, 2021|archive-url=https://web.archive.org/web/20210729031036/https://axs.berkeley.edu/about.html|url-status=dead}}</ref>

Lewis' graduate advisees at Berkeley went on to be exceptionally successful with the [[Nobel Committee]]. 14 [[Nobel Prize|Nobel prizes]] were eventually awarded to the men he took as students.<ref>{{Cite web |last=Physics |first=American Institute of |date=2021-09-24 |title=Willard Libby - Session I |url=https://www.aip.org/history-programs/niels-bohr-library/oral-histories/4743-1 |access-date=2023-08-17 |website=www.aip.org |language=en}}</ref> The best-known of these include [[Harold Urey]] (1934 Nobel Prize), [[William F. Giauque]] (1949 Nobel Prize), [[Glenn T. Seaborg]] (1951 Nobel Prize), [[Willard Libby]] (1960 Nobel Prize), [[Melvin Calvin]] (1961 Nobel Prize).<ref name=":1" /><ref name=":6">{{Cite web|url=https://www.nobelprize.org/prizes/chemistry/1949/giauque/lecture/|title=The Nobel Prize in Chemistry 1949|website=NobelPrize.org|language=en-US|access-date=2019-03-09}}</ref><ref name=":7">{{Cite web|url=https://www.mediatheque.lindau-nobel.org/research-profile/laureate-libby|title=Research Profile - Willard Frank Libby|website=Lindau Nobel Mediatheque|language=en|access-date=2019-03-09}}</ref> Due to his efforts, the college of chemistry at Berkeley became one of the top chemistry centers in the world.<ref name=":1" /><ref name=":8">{{Cite web|url=https://lemelson.mit.edu/resources/gilbert-newton-lewis|title=Gilbert Newton Lewis {{!}} Lemelson-MIT Program|website=lemelson.mit.edu|access-date=2019-03-09|archive-date=2020-04-11|archive-url=https://web.archive.org/web/20200411010110/https://lemelson.mit.edu/resources/gilbert-newton-lewis|url-status=dead}}</ref>

While at Berkeley he also refused entry to women, including preventing [[Margaret Melhase]] from conducting graduate studies.<ref name="SFGATE">{{cite web |last1=Davidson |first1=Keay |title=Margaret Fuchs -- worked on secret atomic bomb project |url=https://www.sfgate.com/bayarea/article/Margaret-Fuchs-worked-on-secret-atomic-bomb-2489618.php |website=SFGATE |date=8 September 2006 |archiveurl=https://web.archive.org/web/20210513204640/https://www.sfgate.com/bayarea/article/Margaret-Fuchs-worked-on-secret-atomic-bomb-2489618.php |archive-date=2021-05-13}}</ref><ref name="PattonArticle">{{Cite journal|last=Patton|first=Dennis D.|date=1999-04-01|title=History Corner: How Cesium-137 Was Discovered by an Undergraduate Student|url=https://jnm.snmjournals.org/content/40/4/18N|journal=Journal of Nuclear Medicine|volume=40|issue=4|pages=18N–31N|issn=0161-5505|pmid=10210206}}</ref> Melhase had previously co-discovered [[Cesium-137]] with Seaborg as an undergraduate. In 1913, he was elected to the [[United States National Academy of Sciences|National Academy of Sciences]].<ref>{{Cite web |title=Gilbert N. Lewis |url=https://www.nasonline.org/member-directory/deceased-members/20000757.html |access-date=2023-10-03 |website=www.nasonline.org}}</ref> He was elected to the [[American Philosophical Society]] in 1918.<ref>{{Cite web |title=APS Member History |url=https://search.amphilsoc.org/memhist/search?creator=Gilbert+N.+Lewis&title=&subject=&subdiv=&mem=&year=&year-max=&dead=&keyword=&smode=advanced |access-date=2023-10-03 |website=search.amphilsoc.org}}</ref> He resigned in 1934, refusing to state the cause for his resignation; it has been speculated that it was due to a dispute over the internal politics of that institution or to the failure of those he had nominated to be elected. His decision to resign may also have been sparked by his resentment over the award of the 1934 Nobel Prize for chemistry to his student, [[Harold Urey]], for his 1931 isolation of [[deuterium]] and the confirmation of its [[Spectral line|spectrum]]. This was a prize Lewis almost certainly felt he should have shared for his efforts to purify and characterize [[heavy water]].<ref>Coffey (2008): 221-22.</ref>

==Death==
On 23 March 1946,<ref>{{cite web |last1=Helmenstine |first1=Todd |title=Today in Science History - March 23 - Gilbert Lewis |url=https://sciencenotes.org/today-in-science-history-march-23-gilbert-lewis/ |website=Science Notes and Projects |access-date=6 August 2020 |date=22 March 2018}}</ref> a graduate student found Lewis's lifeless body under a laboratory workbench at Berkeley. Lewis had been working on an experiment with liquid [[hydrogen cyanide]], and deadly fumes from a broken line had leaked into the laboratory. The coroner ruled that the cause of death was [[coronary artery disease]], because of a lack of any signs of cyanosis,<ref name="Coffey">Coffey (2008): 310-15.</ref>  but some believe that it may have been a suicide. Berkeley Emeritus Professor William Jolly, who reported the various views on Lewis's death in his 1987 history of UC Berkeley's College of Chemistry, ''From Retorts to Lasers'', wrote that a higher-up in the department believed that Lewis had committed suicide.<ref name=":5" />

If Lewis's death was indeed a suicide, a possible explanation was depression brought on by a lunch with [[Irving Langmuir]]. Langmuir and Lewis had a long rivalry, dating back to Langmuir's extensions of Lewis's theory of the chemical bond. Langmuir had been awarded the 1932 Nobel Prize in chemistry for his work on [[surface chemistry]], while Lewis had not received the Prize despite having been nominated 41 times.<ref name="NobelPrize" /> On the day of Lewis's death, Langmuir and Lewis had met for lunch at Berkeley, a meeting that Michael Kasha recalled only years later.<ref name="Coffey" /> Associates reported that Lewis came back from lunch in a dark mood, played a morose game of bridge with some colleagues, then went back to work in his lab. An hour later, he was found dead. Langmuir's papers at the [[Library of Congress]] confirm that he had been on the Berkeley campus that day to receive an honorary degree.

Lewis Hall at Berkeley, built in 1948, is named in his honor.<ref name=":4">{{Cite web|url=https://access.berkeley.edu/lewis-hall|title=Lewis Hall {{!}} Campus Access Services|website=access.berkeley.edu|access-date=2019-03-09}}</ref>

== Scientific achievements ==
{{more footnotes needed|sect|date=August 2020}}

===Thermodynamics===
Most of Lewis’ lasting interests originated during his Harvard years. The most important was thermodynamics, a subject in which Richards was very active at that time. Although most of the important thermodynamic relations were known by 1895, they were seen as isolated equations, and had not yet been rationalized as a logical system, from which, given one relation, the rest could be derived. Moreover, these relations were inexact, applying only to ideal chemical systems. These were two outstanding problems of theoretical thermodynamics. In two long and ambitious theoretical papers in 1900 and 1901, Lewis tried to provide a solution. Lewis introduced the thermodynamic concept of [[activity (chemistry)|activity]] and coined the term "[[fugacity]]".<ref>{{cite journal |last1=Lewis |first1=Gilbert Newton |title=The law of physico-chemical change |journal=Proceedings of the American Academy of Arts and Sciences |date=June 1901 |volume=37 |issue=3 |pages=49–69 |url=https://babel.hathitrust.org/cgi/pt?id=njp.32101050586062;view=1up;seq=57 |doi=10.2307/20021635 |jstor=20021635 |url-access=subscription }} ; the term "fugacity" is coined on p. 54.</ref><ref>{{cite journal |last1=Lewis |first1=Gilbert Newton |title=Outlines of a new system of thermodynamic chemistry |journal=Proceedings of the American Academy of Arts and Sciences |date=1907 |volume=43 |issue=7 |pages=259–293 |url=https://babel.hathitrust.org/cgi/pt?id=njp.32101050586120;view=1up;seq=275|doi=10.2307/20022322 |jstor=20022322 |url-access=subscription }} ; the term "activity" is defined on p. 262.</ref><ref>{{cite journal |last1=Pitzer |first1=Kenneth S. |title=Gilbert N. Lewis and the thermodynamics of strong electrolytes |journal=Journal of Chemical Education |date=February 1984 |volume=61 |issue=2 |pages=104–107 |doi=10.1021/ed061p104 |bibcode=1984JChEd..61..104P |url=https://escholarship.org/content/qt4x23w27c/qt4x23w27c.pdf?t=p0fw58 |doi-access=free }}</ref> His new idea of fugacity, or "escaping tendency",<ref>{{cite journal |last1=Lewis |first1=Gilbert Newton |title=A new conception of thermal pressure and a theory of solutions |journal=Proceedings of the American Academy of Arts and Sciences |date=1900 |volume=36 |issue=9 |pages=145–168 |url=https://babel.hathitrust.org/cgi/pt?id=njp.32101050586054;view=1up;seq=165|doi=10.2307/20020988 |jstor=20020988 |url-access=subscription }} The term "escaping tendency" is introduced on p. 148, where it is represented by the Greek letter ''ψ'' ; ''ψ'' is defined for ideal gases on p. 156.</ref> was a function with the dimensions of [[pressure]] which expressed the tendency of a substance to pass from one chemical phase to another. Lewis believed that fugacity was the fundamental principle from which a system of real thermodynamic relations could be derived. This hope was not realized, though fugacity did find a lasting place in the description of real gases.

Lewis’ early papers also reveal an unusually advanced awareness of [[Josiah Willard Gibbs|J. W. Gibbs's]] and [[Pierre Duhem|P. Duhem's]] ideas of free energy and [[thermodynamic potential]]. These ideas were well known to physicists and mathematicians, but not to most practical chemists, who regarded them as abstruse and inapplicable to chemical systems. Most chemists relied on the familiar thermodynamics of heat (enthalpy) of [[Marcellin Berthelot|Berthelot]], [[Wilhelm Ostwald|Ostwald]], and [[Jacobus Henricus van 't Hoff|Van ’t Hoff]], and the [[calorimetry|calorimetric]] school. Heat of reaction is not, of course, a measure of the tendency of chemical changes to occur, and Lewis realized that only free energy and entropy could provide an exact chemical thermodynamics. He derived free energy from fugacity; he tried, without success, to obtain an exact expression for the [[entropy]] function, which in 1901 had not been defined at low temperatures. Richards too tried and failed, and not until Nernst succeeded in 1907 was it possible to calculate entropies unambiguously. Although Lewis’ fugacity-based system did not last, his early interest in [[Thermodynamic free energy|free energy]] and entropy proved most fruitful, and much of his career was devoted to making these useful concepts accessible to practical chemists.

At Harvard, Lewis also wrote a theoretical paper on the thermodynamics of [[blackbody radiation]] in which he postulated that light has a pressure. He later revealed that he had been discouraged from pursuing this idea by his older, more conservative colleagues, who were unaware that [[Wilhelm Wien]] and others were successfully pursuing the same line of thought. Lewis’ paper remained unpublished; but his interest in radiation and [[quantum mechanics|quantum theory]], and (later) in [[theory of relativity|relativity]], sprang from this early, aborted effort. From the start of his career, Lewis regarded himself as both chemist and physicist.

===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|url-access=subscription }}</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]].

===Acids and bases===
{{Main|Lewis acids and bases}}

In 1923, he formulated the electron-pair theory of [[acid–base reaction]]s. In this theory of [[acid]]s and [[base (chemistry)|base]]s, a "Lewis acid" is an ''electron-pair acceptor'' and a "Lewis base" is an ''electron-pair donor''.<ref>{{cite book |last1=Lewis |first1=Gilbert Newton |title=Valence and the Structure of Atoms and Molecules |date=1923 |publisher=Chemical Catalog Company |location=New York|page=142 |url=https://babel.hathitrust.org/cgi/pt?id=uc1.b3219599;view=1up;seq=148|quote = We are inclined to think of substances as possessing acid or basic properties, without having a particular solvent in mind.  It seems to me that with complete generality we may say that ''a basic substance is one which has a lone pair of electrons which may be used to complete the stable group of another atom'', and that ''an acid substance is one which can employ a lone pair from another molecule'' in completing the stable group of one of its own atoms.  In other words, the basic substance furnishes a pair of electrons for a chemical bond, the acid substance accepts such a pair.}}</ref> This year he also published a monograph on his theories of the chemical bond.<ref>Lewis, G. N. (1926) ''Valence and the Nature of the Chemical Bond''. Chemical Catalog Company.</ref>

Based on work by [[Josiah Willard Gibbs|J. Willard Gibbs]], it was known that chemical reactions proceeded to an [[Chemical equilibrium|equilibrium]] determined by the [[Thermodynamic free energy|free energy]] of the substances taking part. Lewis spent 25 years determining free energies of various substances. In 1923 he and [[Merle Randall]] published the results of this study,<ref>Lewis, G. N. and [[Merle Randall]] (1923) ''Thermodynamics and the Free Energies of Chemical Substances''. McGraw-Hill.</ref> which helped formalize modern [[chemical thermodynamics]].

===Heavy water===
Lewis was the first to produce a pure sample of deuterium oxide ([[heavy water]]) in 1933<ref>{{Cite journal| pages = 341| year = 1933 | doi = 10.1063/1.1749300| last2 =  MacDonald| first1 = G. N.| volume = 1| last1 = Lewis| journal = The Journal of Chemical Physics | first2 = R. T.| title = Concentration of H<sub>2</sub> Isotope| issue = 6|bibcode = 1933JChPh...1..341L }}</ref> and the first to study survival and growth of life forms in heavy water.<ref>{{Cite journal| title = The biochemistry of water containing hydrogen isotope| last1 = Lewis| first1 = G. N.| journal = Journal of the American Chemical Society| volume = 55| issue = 8| pages = 3503–3504| year = 1933 | doi = 10.1021/ja01335a509| bibcode = 1933JAChS..55.3503L}}</ref><ref>{{Cite journal| doi = 10.1126/science.79.2042.151| pmid = 17788137| year = 1934| last1 = Lewis | first1 = G. N.| title = The biology of heavy water| volume = 79| issue = 2042| pages = 151–153| journal = Science   |bibcode = 1934Sci....79..151L | s2cid = 4106325}}</ref> By accelerating [[deuteron]]s (deuterium [[atomic nucleus|nuclei]]) in [[Ernest Lawrence|Ernest O. Lawrence's]] [[cyclotron]], he was able to study many of the properties of atomic nuclei.<ref>{{Cite book|url=https://www.sciencedirect.com/topics/earth-and-planetary-sciences/deuteron|title = Deuteron - an overview &#124; ScienceDirect Topics| chapter=Radioactivity Hall of Fame–Part VIII | date=2007 | pages=497–528 | publisher=Elsevier | isbn=978-0-444-52715-8 }}</ref> During the 1930s, he was mentor to [[Glenn T. Seaborg]], who was retained for post-doctoral work as Lewis' personal research assistant. Seaborg went on to win the 1951 [[Nobel Prize]] in Chemistry and have the element [[seaborgium]] named in his honor while he was still alive.

=== O<sub>4</sub> Tetraoxygen ===
In 1924, by studying the [[magnetism|magnetic]] properties of solutions of [[oxygen]] in [[liquid]] [[nitrogen]], Lewis found that O<sub>4</sub> molecules were formed.<ref>{{Cite journal|last=Lewis|first=Gilbert N.|date=1924-09-01|title=The magnetism of oxygen and the molecule O<sub>4</sub>|journal=Journal of the American Chemical Society|volume=46|issue=9|pages=2027–2032|doi=10.1021/ja01674a008|bibcode=1924JAChS..46.2027L |issn=0002-7863}}</ref> This was the first evidence for [[tetraoxygen|tetratomic oxygen]].

=== Relativity and quantum physics ===

In 1908 he published the first of several papers on [[theory of relativity|relativity]], in which he derived the [[mass]]-[[energy]] relationship in a different way from [[Albert Einstein]]'s derivation.<ref name=":9">{{Cite journal|author=Lewis, G. N.|year=1908|title=A revision of the Fundamental Laws of Matter and Energy|journal=Philosophical Magazine|volume=16|issue=95|pages=705–717|doi=10.1080/14786441108636549|title-link=s:A revision of the Fundamental Laws of Matter and Energy}}</ref> In 1909, he and [[Richard C. Tolman]] combined his methods with [[principle of relativity|special relativity]].<ref>{{Cite journal|author=Lewis, G. N. & [[Richard C. Tolman]]|year=1909|title=The Principle of Relativity, and Non-Newtonian Mechanics|journal=Proceedings of the American Academy of Arts and Sciences|volume=44|issue=25|pages=709–26|doi=10.2307/20022495|jstor=20022495|title-link=s:The Principle of Relativity, and Non-Newtonian Mechanics}}</ref> In 1912 Lewis and [[Edwin Bidwell Wilson]] presented a major work in mathematical physics that not only applied [[synthetic geometry]] to the study of [[spacetime]], but also noted the identity of a spacetime [[squeeze mapping]] and a [[Lorentz transformation]].<ref>{{cite journal|last1=Wilson|first1=Edwin B.|last2=Lewis|first2=Gilbert N.|year=1912|title=The Space-time Manifold of Relativity. The Non-Euclidean Geometry of Mechanics and Electromagnetics|journal=Proceedings of the American Academy of Arts and Sciences|volume=48|issue=11|pages=387–507|doi=10.2307/20022840|jstor=20022840}}</ref><ref>[https://web.archive.org/web/20091027012400/http://ca.geocities.com/cocklebio/synsptm.html Synthetic Spacetime], a digest of the axioms used, and theorems proved, by Wilson and Lewis. Archived by [[WebCite]]</ref>

In 1926, he coined the term "[[photon]]" for the smallest unit of radiant energy (light). Actually, the outcome of his letter to ''[[Nature (journal)|Nature]]'' was not what he had intended.<ref>
{{cite journal|author=Lewis, G.N.|year=1926|title=The conservation of photons|url=https://www.nature.com/articles/118874a0|journal=[[Nature (journal)|Nature]]|volume=118|issue=2981|pages=874–875|bibcode=1926Natur.118..874L|doi=10.1038/118874a0|s2cid=4110026|url-access=subscription}}</ref> In the letter, he proposed a photon being a structural element, not [[energy]]. He insisted on the need for a new variable, ''the number of photons''. Although his theory differed from the [[photon|quantum theory of light]] introduced by [[Albert Einstein]] in 1905, his name was adopted for what Einstein had called a '''light quantum''' (Lichtquant in German).

===Other achievements===
In 1921, Lewis was the first to propose an empirical equation describing the failure of [[strong electrolyte]]s to obey the [[law of mass action]], a problem that had perplexed physical chemists for twenty years.<ref>{{cite journal|last1=Lewis|first1=Gilbert N.|last2=Randall|first2=Merle|date=1921|title=The activity coefficient of strong electrolytes|url=https://babel.hathitrust.org/cgi/pt?id=mdp.39015018181431;view=1up;seq=1144|journal=Journal of the American Chemical Society|volume=43|issue=5|pages=1112–1154|doi=10.1021/ja01438a014|bibcode=1921JAChS..43.1112L |url-access=subscription}} The term "ionic strength" is introduced on p. 1140.</ref> His empirical equations for what he called [[ionic strength]] were later confirmed to be in accord with the [[Debye–Hückel equation]] for strong electrolytes, published in 1923.

Over the course of his career, Lewis published on many other subjects besides those mentioned in this entry, ranging from the nature of [[light]] quanta to the [[economics]] of price stabilization. In the last years of his life, Lewis and graduate student [[Michael Kasha]], his last research associate, established that [[phosphorescence]] of [[organic chemistry|organic]] molecules involves emission of light from one electron in an excited [[triplet state]] (a state in which two electrons have their [[Spin (physics)|spin vector]]s oriented in the ''same'' direction, but in different orbitals) and measured the [[paramagnetism]] of this triplet state.<ref>{{cite journal|last1=Lewis|first1=Gilbert N.|last2=Kasha|first2=M.|year=1944|title=Phosphorescence and the Triplet State|journal=Journal of the American Chemical Society|volume=66|issue=12|pages=2100–2116|doi=10.1021/ja01240a030|bibcode=1944JAChS..66.2100L }}</ref>

==See also==
{{wikisource author}}
*[[History of molecular theory]]

==References==
{{reflist|30em}}

==Further reading==
*Coffey, Patrick (2008) ''Cathedrals of Science: The Personalities and Rivalries That Made Modern Chemistry''. Oxford University Press. {{ISBN|978-0-19-532134-0}}

==External links==
*{{Commons category-inline}}
*[http://osulibrary.oregonstate.edu/specialcollections/coll/pauling/bond/people/lewis.html Key Participants: G. N. Lewis] - ''Linus Pauling and the Nature of the Chemical Bond: A Documentary History''
*Eric Scerri, ''The Periodic Table, Its Story and Its Significance'', Oxford University Press, 2007, see chapter 8 especially
*[http://www.nasonline.org/publications/biographical-memoirs/memoir-pdfs/lewis-gilbert-n.pdf National Academy of Sciences Biographical Memoir]

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[[Category:Members of the United States National Academy of Sciences]]
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