rare metallic element, 1797, named 1789 in Modern Latin by its discoverer, German chemist and mineralogist Martin Heinrich Klaproth (1743-1817), for the recently found planet Uranus (q.v.).
uranium u·ra·ni·um (yu-rā'nē-əm)
n.
Symbol U
An easily oxidized radioactive toxic metallic element having 16 known isotopes, of which U 238 is the most naturally abundant. Atomic number 92; atomic weight 238.03; melting point 1,135°C; boiling point 4,151°C; specific gravity 18.95; valence 2, 3, 4, 5, 6.
uranium (y-rā'nē-əm) Symbol U A heavy, silvery-white, highly toxic, radioactive metallic element of the actinide series. It has 14 known isotopes, of which U 238 is the most naturally abundant, occurring in several minerals. Fissionable isotopes, especially U 235, are used in nuclear reactors and nuclear weapons. Atomic number 92; atomic weight 238.03; melting point 1,132°C; boiling point 3,818°C; specific gravity 18.95; valence 2, 3, 4, 5, 6. See Periodic Table. |
A chemical element that is naturally radioactive. An isotope of uranium, uranium 235, is the main fuel for nuclear reactors and atomic bombs. Its symbol is U. (See fission and chain reaction.)