Any element lying beyond uranium in the periodic table, i.e. any element of atomic number greater than 92. The best known transuranic elements are those in the actinide (atomic numbers 89 to 103). Neptunium was the first of the transuranic elements to be produced in 1940 by the US physicist Edward McMillan and US physical chemist Philip Abelson, who bombarded uranium with neutrons in a synchrocyclotron.
Except for the plutonium isotopes Pu-244 (half-life about 80 million years) and Pu-239 (continuous reformation in rock containing uranium by neutron capture in U-238 by neutrons from the spontaneous fission of U-238) detected in very small quantities, all transuranic elements must be produced artificially by suitable nuclear reactions, usually involving bombardment with neutrons or alpha particles. All are radioactive.
Related categories ATOMIC AND NUCLEAR PHYSICS
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