neptunium

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neptunium (symbol Np) Radioactive metallic element, the first of the transuranic elements of the actinide series. Discovered in 1940 by US physicists Edwin McMillan and Philip Abelson (1913– ), this silvery element is found in small amounts in uranium ores, and is obtained as a by-product in nuclear reactors. Properties: at.no. 93; r.a.m. 237.0482; r.d. 20.25; m.p. 640°C (1,184°F); b.p. 3,902°C (7,056°F); most stable isotope 237Np (half-life 2.2 million years).

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