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neptunium

neptunium definition

☆ nep·tu·nium (nep to̵̅o̅′nē əm, -tyo̵̅o̅′-)

noun

a silver-colored, radioactive, metallic chemical element, one of the actinides, produced by bombarding uranium atoms with neutrons: symbol, Np; at. no., 93

Etymology: ModL < Neptunus, Neptune + -ium: so named by Edwin Mattison McMillan & P. Abelson (1913-2004), U.S. physicists, because its at. no. is next after uranium's, as the planet Neptune is next beyond Uranus

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