Lewis, Gilbert Newton, 1875–1946, American chemist, b. Weymouth, Mass., grad. Harvard (B.A., 1896; Ph.D., 1899). He taught at Harvard and at the Massachusetts Institute of Technology (1907–12) and from 1912 was professor of physical chemistry and dean of the college of chemistry, Univ. of California. His recognition of the importance of the electron pair bond led to a revision of the theory of valence. He also made special studies in thermodynamics, formulated the Lewis theory of acids and bases, and with Harold C. Urey, a graduate student of his, discovered heavy water (1932). He wrote Valence and the Structure of Atoms and Molecules (1923).