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Lewis, Gilbert Newton

electrons pair chemical ideas

(1875–1946) US physical chemist: major contributor to theory of chemical bonding.

A Harvard graduate, Lewis studied in Germany for 2 years and then went to the Philippines as a government chemist. From 1905–12 he was at the Massachusetts Institute of Technology and then spent the rest of his career at the University of California at Berkeley.

Lewis developed ideas on chemical thermodynamics and made the experimental measurements that allowed the outcome of a range of chemical reactions to be predicted by calculation. He was also a pioneer in taking ideas concerning electrons from physics and applying them in chemistry. From 1902 he shaped his ideas on this subject and published them in 1916; they were then publicized and expanded and later . In developed form (as in his work of 1923) Lewis’s ideas focused on the arrangement of electrons around atomic nuclei. He assumed that elements heavier than the lightest two (H and He) had a pair of electrons surrounding the nucleus, with further electrons (in number to balance the nuclear charge) in groups, with a group of eight as especially stable. Bonding between atoms of the lighter elements occurred in such a way that atoms gained or lost outer electrons to create octets, either by transfer (electrovalence) or by sharing (covalence). Noting that nearly all chemical compounds contain an even number of electrons, he concluded that the electron pair is especially important, and a shared pair can be equated with a covalent bond. The familiar ‘dot diagrams’ showing the electronic structure of many simple compounds are devised on this simple theory.

Lewis also saw the importance of electron pairs in another context. He defined a base as a substance that has a pair that can be used to complete the stable shell of another atom; and an acid as a substance able to accept a pair from another atom to form a stable group of electrons. This very general concept of Lewis acids and bases has proved valuable.

Probably no man did more to advance chemical theory in the 20th-c, but he was always a diffident as well as an attractive and engaging person, with an unorthodox mind.

Lewis, Jenifer (1957–) [next] [back] Leviathan

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