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Seaborg, Glenn Theodore

uranium elements atomic transuranic

(1912–99) US nuclear chemist: discoverer of transuranic elements of the actinide series.

After he obtained his PhD in chemistry at the University of California at Berkeley, in 1937, Seaborg worked with , joined the staff and became professor of chemistry in 1945. He was to be linked with the University of California for the rest of his career, with absences on government work during the Second World War and from 1961–71, when he was chairman of the US Atomic Energy Commission.

The heaviest element that occurs in nature in fair quantity is uranium, with atomic number 92. In the 1930s more than one research group bombarded uranium with neutrons and examined the results, and believed that elements heavier than uranium (‘transuranic elements’) had been formed. Then came the proposal in 1939 by that fission had occurred; the uranium nucleus accepts the neutron and then breaks up to give two or more nuclei of middle-range mass. But in 1940 and P Abelson (1913– ) showed that transuranic elements can in fact be made; some of the uranium nuclei struck by neutrons do not undergo fission but form a new element, the first to be discovered beyond uranium, which they named neptunium. From 1940 Seaborg became involved in the work, found a new way of making an isotope of neptunium (atomic number 93) and went on to extend the research by making heavier transuranic elements. Seaborg was a key figure in the work which resulted in making and identifying nine of them, from plutonium (atomic number 94) through to nobelium (102). In much of this a cyclotron was used to generate the bombarding particles, and the work was directed in part to study the basic chemistry of the new elements, and in part to produce an atomic bomb (of the first two of these, exploded in 1945, one was fuelled by uranium and one by plutonium). Seaborg realized in 1944 that the series of elements from actinium (89) onwards, could be classed within the periodic table as a new transition series, akin to the lanthanides; he named the new series (now seen as numbers 89–103) the actinides. They are all radioactive and the transuranic members (numbers 93 onwards) occur only in minute traces in nature. Seaborg and McMillan shared the Nobel Prize for chemistry in 1951.

Sears, Clara Endicott (1863–1960) - U.S. History [next] [back] Scottron, Samuel R.(1843–1905) - Inventor, entrepreneur, Inventions, Chronology

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