Gilbert N Lewis

Gilbert Newton Lewis (Weymouth, Massachusetts, October 23, 1875-Berkeley, March 23, 1946) was an American physical chemist, famous for his work on the so-called " Lewis structure" or "dot plots". He is also remembered for devising the concept of covalent bonding and for coining the term photon.

Biography

Lewis was educated at home until he was 8 years old, attending public school until he was 14, at which time he entered the University of Nebraska and three years later began studying at Harvard University, where he showed interest in economics. However, he concentrated on chemistry, obtaining his baccalaureate in 1896 and his doctorate in 1898. He developed an intense work on issues related mainly to this discipline, publishing numerous articles with the results of his research.

He died at age 70 of a heart attack while working in his laboratory in Berkeley. He is indebted to the study of the peripheral electrons of atoms, from which he deduced, in 1916, an interpretation of covalence. He also proposed, in 1926, the name photon for the quantum of electromagnetic energy.

Professional activity

After earning his Ph.D. (Professional Doctorate) he remained as an instructor for a year with which before traveling on fellowship, studying with the physical chemist Wilhelm Ostwald in Leipzig and with Walther Nernst in Göttingen. He returned to Harvard where he remained for another three years, and in 1904 he left the university to take up the post of superintendent and measurements at the Philippine Islands Bureau of Science, in Manila.

The following year he returned to Cambridge, when the Massachusetts Institute of Technology (MIT) asked him to join a group dedicated to physical chemistry led by Arthur Amos Noyes. In 1907 he became an assistant professor, in 1908 as an adjunct professor, and in 1911 as a full professor. In 1912 he left MIT to work as Professor of Physical Chemistry and Dean of the College of Chemistry at the University of California.

In 1908 he published the first of several papers on the Theory of Relativity, in which he deduced the mass-energy relationship in a different way than Einstein.

In 1916 he formulated the model of the cubic atom, and the idea that a covalent bond consists of a shared pair of electrons and created the term odd molecule when an electron is not shared. His ideas were developed by Irving Langmuir and served as inspiration for the studies of Linus Pauling.

In the same year, together with Max Trautz, they developed the theory of collisions, in which they explain the energy required for a chemical reaction to occur.

In addition, in that year he enunciated the important octet rule.

In 1919, studying the magnetic properties of oxygen solutions in liquid nitrogen, he found that an O₄ molecule had formed. This was the first evidence for tetraatomic oxygen.

In 1923, he formulated the electron pair theory for acid-base reactions, allowing Lewis acids and bases to be distinguished.

Thanks to the work of Josiah Willard Gibbs, it was known that chemical reactions tend to an equilibrium determined by the free energy of the intervening substances. Lewis spent 25 years determining the free energy of various substances, and in 1923 he and Merle Randall published the results of the study and formalized thermodynamic chemistry.

In 1926 he coined the term "photon" for the smallest unit of radiant energy.

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

In the last years of his life he proved that the phosphorescence of organic molecules obeys the state of an excited triplet and measured its magnetic properties.

He has published numerous articles on a wide range of topics, from light quanta to the economics of price stabilization.

Although he was nominated 42 times, Lewis never won the Nobel Prize in Chemistry. On March 23, 1946, Lewis was found dead in his Berkeley laboratory where he had been working with hydrocyanic acid, spreading rumors that his cause of death may have been suicide. After Lewis's death, his children followed his father's career in chemistry.

Scientific achievements

Thermodynamics

Most of Lewis's long-lasting interests originated during his years at Harvard. The most important was thermodynamics, a subject in which Richards was very active at the time. Although most of the important thermodynamic relationships were known by 1895, they were considered isolated equations, and had not yet been rationalized into a logical system, from which, given one relationship, the rest could be derived. Furthermore, these relationships were inexact and only applied 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 and coined the term "fugacity". His new idea of fugacity, or "escape tendency", was a function with the dimensions of the pressure that 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 did not come true, although fugacity did find a lasting place in the description of real gases.

Lewis' early work also reveals an unusually advanced knowledge of J. W. Gibbs and P. Duhem's ideas on free energy and thermodynamic potential. These ideas were well known to physicists and mathematicians, but not to most practical chemists, who considered them abstruse and inapplicable to chemical systems. Most chemists relied on the well-known thermodynamics of heat (enthalpy) from Berthelot, Ostwald, and Van't Hoff, and the calorimetric school. The heat of reaction is, of course, not a measure of the tendency of chemical changes to occur, and Lewis realized that only free energy and entropy could provide accurate chemical thermodynamics. He derived free energy from transience; he tried, without success, to obtain an exact expression for the entropy function, which in 1901 had not been defined at low temperatures. Richards also tried and failed, and it was not until Nernst succeeded in 1907 that entropy could be calculated unequivocally. Although Lewis's fugacity-based system did not endure, his early interest in 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 his older and more conservative colleagues had dissuaded him from pursuing this idea, as they were unaware that Wilhelm Wien and others were successfully following the same line of thought. Lewis's paper was not published, but his interest in radiation and quantum theory, and (later) in relativity, grew out of this first abortive effort. From the beginning of his career, Lewis considered himself as much a chemist as a physicist.

Valence Theory

Around 1902, Lewis began using previously unpublished drawings of cubic atoms in his lecture notes, in which the corners of the cube represented possible positions of the electron. These notes were later cited by Lewis in his classic 1916 paper on chemical bonding as the first expression of his ideas.

A third important interest that arose during Lewis's years at Harvard was his theory of valence. In 1902, while trying to explain the valence laws to his students, Lewis conceived the idea that atoms were made up of a concentric series of cubes with electrons at each corner. This "cubic atom" it explained the cycle of eight elements in the periodic table and agreed 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, but Lewis's version of this theory was the only one that was embodied in a concrete atomic model. Once again, Lewis's theory did not interest his Harvard mentors, who, like most American chemists of the day, had no taste for such speculations. Lewis did not publish his theory of the cubic atom, but in 1916 it became an important part of his theory of shared pair-electron bonding.

In 1916, he published his classic article on chemical bonding "The Atom and the Molecule" in which he formulated the idea of what would become known as a covalent bond, consisting of a shared pair of electrons, and defined the term odd molecule (the modern term is free radical) when an electron is not shared. He included what became known as the Lewis dot structure, as well as the cubic atom model. These ideas about chemical bonding were expanded upon by Irving Langmuir and became the inspiration for Linus Pauling's studies of the nature of chemical bonding.

Acids and Bases

In 1923, he formulated the electron pair theory of acid-base reactions. In this theory of acids and bases, a "Lewis acid" is an "electron pair acceptor" and a "Lewis base" it is an "electron pair donor". This year he also published a monograph on his theories of chemical bonding.

Based on the work of Josiah Willard Gibbs, it was known that chemical reactions proceeded to a chemical equilibrium determined by the thermodynamic free energy of the substances involved. Lewis spent 25 years determining the free energies of various substances. In 1923, he and Merle Randall published the results of this study, which helped formalize modern chemical thermodynamics.

Heavy water

Lewis was the first to produce a pure sample of deuterium oxide (heavy water) in 1933 and the first to study the survival and growth of life forms in heavy water. By accelerating deuteron nuclei in a Ernest Lawrence's cyclotron, he was able to study many of the properties of atomic nuclei. During the 1930s, he was a mentor to Glenn T. Seaborg, who was hired for his postdoctoral work as Lewis' personal research assistant. Seaborg went on to win the 1951 Nobel Prize in Chemistry and was honored to have the element seaborgium named after him while he was still alive.

O4 tetra oxygen

In 1924, while studying the magnetic properties of solutions of oxygen in liquid nitrogen, Lewis discovered that O₄ molecules were formed. This was the first evidence for tetratomous oxygen.

Relativity and quantum physics

In 1908 he published the first of several papers on relativity, in which he derived the mass-energy relationship in a different way than Albert Einstein. derivation. In 1909, he and Richard C. Tolman combined their methods with the principle of special relativity. In 1912 Lewis and Edwin Bidwell Wilson pr presented important work in mathematical physics that not only applied synthetic geometry to the study of space -time, but also noted the identity of a compressed spacetime mapping and a Lorentz transformation.

In 1926, he coined the term "photon" for the smallest unit of radiant energy (light). Actually, the result of his letter to Nature was not what he intended.In the letter, he proposed that a photon is a structural element, not energy. He insisted on the need for a new variable, the number of photons. Although his theory differed from the quantum theory of light introduced by Albert Einstein in 1905, his name was adopted by what Einstein had called a light quantum (Lichtquant in German).

Other Achievements

In 1921, Lewis was the first to propose an empirical equation describing why strong electrolytes did not obey the law of mass action, a problem that had puzzled chemical physicists for twenty years. It was later confirmed that his empirical equations for what he called ionic strength were in agreement with the Debye-Hückel equation for strong electrolytes, published in 1923.

Throughout his career, Lewis has published on many other topics than those mentioned here, 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 late research associate, established that the phosphorescence of organic molecules involves the emission of light from an electron in an excited triplet state (a state in which two electrons have their spins oriented in the same direction, but in different orbitals) and measured the paramagnetism of this triplet state.

Eponymy

• Moon crater Lewis carries this name in his memory.