| 释义 |
ura·nium
\yəˈrānēəm, yüˈr- also -nyəm\ noun
(-s)
Etymology: New Latin, from Uranus, seventh planet from the sun discovered in the same decade as uranium (after Uranus, in Greco-Roman mythology the personification of heaven and husband of Earth, from Latin, from Greek Ouranos, from ouranos sky, heaven) + New Latin -ium
: a lustrous silvery heavy radioactive polyvalent metallic element of the actinide series that occurs in concentrated form in pitchblende, carnotite, and autunite and in traces of 0.2 to 200 parts per million in most igneous rocks, phosphate rocks, lignites, and oil shales, that is prepared from its halides by reducton with alkali or alkaline earth metals or from its oxides by reduction with hot carbon, aluminum, or calcium, that exists naturally as a mixture of three isotopes of mass numbers 238, 235, and 234 in the proportions 99.28 percent, 0.71 percent, and 0.006 percent respectively, that undergoes very slow radioactive decay and captures neutrons in a nuclear reactor to produce a heavier isotope of mass number 239 which decomposes by beta emissions into neptunium and then plutonium, and that is used primarily in atomic energy programs to sustain chain-reaction piles, to provide a source of the light isotope uranium 235, and to make plutonium — symbol U; see thorium, uranium series; see element table |