Gilbert Newton Lewis was the first American physical chemist to produce a pure sample of deuterium oxide (heavy water) in 1933. Heavy water is used in certain types of nuclear reactors where it acts as a neutron moderator to slow down neutrons so that they can react with the uranium in the reactor. Lewis also published influential work in chemical bonding, the magnetic properties of solutions of oxygen in liquid nitrogen, electron pair theory, and chemical thermodynamics. He coined the term "photon" for the smallest unit of radiant energy in 1926. In 1913, he was elected to the National Academy of Sciences, but in 1934 he resigned in a dispute over the internal politics of that institution. His decision to resign may have been sparked by resentment over the award of the 1934 Nobel Prize for chemistry to his student, Harold Urey, for the discovery of deuterium, a prize Lewis almost certainly felt he should have shared for his work on purification and characterization of heavy water.

After earning his Ph.D. at Harvard under the direction of Theodore Richards, Lewis stayed as an instructor for a year before taking a traveling fellowship, studying under the physical chemists Wilhelm Ostwald at Leipzig and Walther Nernst at Göttingen.

About 1902 Lewis started to use unpublished drawings of cubical atoms in his lecture notes, in which the corners of the cube represented possible electron positions.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.

In 1908 he published the first of several papers on relativity, in which he derived the mass-energy relationship in a different way from Albert Einstein's derivation. And in 1909 he combined his methods with the principle of relativity. He also introduced the thermodynamic concept of activity and coined the term "fugacity”.

In 1916, he published his classic paper on chemical bonding, 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 dot structures as well as the cubical atom model. These ideas on chemical bonding were expanded upon by Irving Langmuir and became the inspiration for the studies on the nature of the chemical bond by Linus Pauling.

In 1919, by studying the magnetic properties of solutions of oxygen in liquid nitrogen, he found that O₄ molecules were formed. This was the first evidence for tetratomic oxygen.

In 1921, Lewis was the first to propose an empirical equation describing the failure of strong electrolytes to obey the law of mass action, a problem that had perplexed physical chemists for twenty years. 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.

In 1923, he formulated the electron-pair theory of acid-base reactions. In the so-called Lewis theory of acids and bases, a "Lewis acid" is an electron-pair acceptor and a "Lewis base" is an electron-pair donor.

Lewis was the first to produce a pure sample of deuterium oxide (heavy water) in 1933. By accelerating deuterons (deuterium nuclei) in Ernest O. Lawrence's cyclotron, he was able to study many of the properties of atomic nuclei. 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.

In the last years of his life, Lewis and graduate student Michael Kasha established that phosphorescence of organic molecules involves an excited triplet state (a state in which electrons that would normally be paired with opposite spins are instead excited to have their spin vectors in the same direction) and measured the magnetic properties of this triplet state.

Lewis never received the Nobel Prize despite 35 nominations.

Sources

• Cleveland, Cutler (Lead Author); Peter Saundry (Topic Editor). 2008. "Lewis, Gilbert Newton." In: Encyclopedia of Earth. Eds. Cutler J. Cleveland (Washington, D.C.: Environmental Information Coalition, National Council for Science and the Environment). [First published in the Encyclopedia of Earth September 15, 2006; Last revised June 19, 2008; Retrieved April 12, 2009]. 
• Wikipedia Contributors, Gilbert N. Lewis, Wikipedia The Free Encyclopedia, Accessed 12 April 2009.