Coulson, Charles Alfred (1910-1974)

English theoretical chemist who developed a molecular orbital theory and the concept of partial valency. He developed many mathematical techniques for solving chemical and physical problems. Coulson was born in Dudley, Yorkshire, and studied at Cambridge. He became professor of theoretical physics at King's College, London, 1947, professor of mathematics at Oxford 1952, and later Oxford's first professor of theoretical chemistry. He was chair of the charity Oxfam 1965-71. The molecular orbital theory that Coulson developed is an extension of atomic quantum theory and deals with 'allowed' states of electrons in association with two or more atomic nuclei, treating a molecule as a whole. He was thus able to explain properly phenomena such as the structure of benzene and other conjugated systems, and invoked what he called partial valency to account for the bonding in such compounds as diborane. Coulson also contributed significantly to the understanding of the solid state (particularly metals), such as the structure of graphite and its 'compounds'. He wrote three best-selling books: Waves 1941, Electricity 1948, and Valence 1952.