Edwin McMillan

Edwin McMillan (1907–1991) was an American physicist who discovered neptunium and helped discover plutonium, the first elements beyond uranium. He shared the 1951 Nobel Prize in Chemistry with Glenn T. Seaborg.

Neptunium: A radioactive chemical element with atomic number 93, discovered by Edwin McMillan and Philip Abelson in 1940. McMillan and Philip Abelson identified this first transuranium element by irradiating uranium.
Uranium-239: A radioactive isotope of uranium that beta decays to neptunium-239. Neutron irradiation created uranium-239, the starting point in McMillan and Abelson's discovery chain.
Philip Abelson: An American physicist and geochemist who co-discovered neptunium with Edwin McMillan in 1940. Abelson's chemical separation and analysis helped establish neptunium's identity.
Transuranium element: A chemical element with an atomic number greater than uranium's 92. Neptunium opened the experimentally confirmed family of elements beyond uranium.
Plutonium: A radioactive chemical element with atomic number 94, first produced and identified in 1940–1941. McMillan initiated the research that led to plutonium's discovery with Glenn T. Seaborg and colleagues.
Neptunium-239: A radioactive isotope of neptunium that beta decays to plutonium-239. Its formation and decay supplied the key evidence for element 93.
Glenn T. Seaborg: An American chemist who co-discovered plutonium and shared the 1951 Nobel Prize in Chemistry with McMillan. Seaborg led the team that identified plutonium after McMillan's initial work on element 94.
Synchrotron: A cyclic particle accelerator that varies its magnetic field in step with the particles' increasing momentum. McMillan independently proposed the phase-stability principle that made practical synchrotrons possible.
Cyclotron: A particle accelerator that uses a magnetic field and alternating electric fields to drive charged particles in expanding spirals. Berkeley cyclotrons supplied the particles used in McMillan's transmutation experiments.
Beta decay: A radioactive decay process in which a nucleus changes a neutron into a proton or vice versa while emitting a beta particle. Beta decay raised the atomic number in the uranium-to-neptunium sequence.

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