Glenn Theodore Seaborg

Glenn Seaborg

Glenn T. Seaborg in 1942, adjusting a Geiger counter. Courtesy Ernest Orlando Lawrence Berkeley National Laboratory.

Glenn Theodore Seaborg (1912–1999) was involved in identifying nine transuranium elements (94 through 102) and served as chairman of the U.S. Atomic Energy Commission (AEC) from 1961 to 1971. In 1951 he shared the Nobel Prize in chemistry with the physicist Edwin M. McMillan.

Born in Michigan, Seaborg earned his bachelor’s degree at the University of California at Los Angeles and his doctorate in chemistry from the University of California at Berkeley. He then served as research assistant to Gilbert Newton Lewis and eventually became chancellor of the university. He worked away from Berkeley during two significant periods: once to participate in the Manhattan Project at the University of Chicago from 1942 to 1946, and then again to chair the AEC—from which he returned to Berkeley.

In 1940 Edwin McMillan, assisted by Philip Abelson (later editor of Science magazine), confirmed and elucidated the phenomenon of nuclear fission announced by Otto Hahn and Fritz Strassmann in 1939. Specifically, he identified element 93, neptunium, among the fission products of uranium, which was bombarded with neutrons produced from deuterons using the small (27-inch) cyclotron at Berkeley. McMillan also predicted the existence of element 94, plutonium, which he expected to find among the products of uranium under direct deuteron bombardment. McMillan, however, was suddenly called away to do war work and eventually joined the program at Los Alamos to build nuclear bombs. Seaborg and his associates took over McMillan’s project.

Glenn T. Seaborg and President John F. Kennedy at Germantown, Maryland, headquarters of the Atomic Energy Commission, 16 February 1961. Courtesy Ernest Orlando Lawrence Berkeley National Laboratory.

Glenn T. Seaborg and President John F. Kennedy at Germantown, Maryland, headquarters of the Atomic Energy Commission, February 16, 1961. Courtesy Ernest Orlando Lawrence Berkeley National Laboratory.

Seaborg and team soon found plutonium with a mass number of 238. Further research led to the production of isotope 239 in early 1941 in very small quantities. Plutonium-239 was shown to be fissionable by bombardment with slow neutrons and therefore became the newest material from which a nuclear bomb could be constructed. Up to that time scientists had known only of uranium-235 for this purpose. Seaborg then joined the Manhattan Project to work on the plan for producing sufficient plutonium-239 for a bomb—the one that was dropped on Nagasaki. Even before the war ended, he turned his attention to the production of further transuranium elements, developing the actinide transition series in the periodic table.

At the AEC, Seaborg became deeply involved in both arms control and nuclear regulatory affairs—attempting to manage the power of the atomic nucleus that his scientific work had revealed. Among chemists he was unusual in writing histories of the epic developments in which he was involved so that the public could be the wiser for his experiences. With Benjamin S. Loeb he wrote a historical series, the first of which was Kennedy, Khrushchev, and the Test Ban (1981).

Hear It Firsthand

The Center for Oral History captures and preserves the stories of notable figures in chemistry and related fields, with over 425 oral histories that deal with various aspects of science, of scientists, and of scientific practices. For more information please visit CHF’s Oral History Program or e-mail oralhistory@

Connect with CHF


Listen to the latest episodes of CHF’s award-winning science podcast.


Historically Grounded Perspectives

The Center for Contemporary History and Policy explores issues ranging from energy to medicine on CHF's blog, Periodic Tabloid.