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铀是人们很熟悉的一种放射性元素,它的比重很大,每立方米金属铀重达18.7吨(铁的比重为7.9吨/米~3),铀元素的化学性质活泼,具有四价、六价两种价态,是一种亲氧亲石元素,所以它的比重虽大,并不沉入地球深处,绝大部分“悬浮”在地壳上部的硅铝层中,以多种形式(简单的氧化物、复杂的络合物或以类质同象组成多种硅酸盐矿物等)出现.现已查明的铀矿物或含铀矿物达两百余种之多,它们散布于地壳的各大类岩石之中.金属铀在空气中极易氧化,温度稍高甚至燃烧,在自然界中,人们从未见到过金属铀,因此,就误认为铀是一种特别稀少的贵重金属.
Uranium is a radioactive element that people are familiar with. Its weight is very high. It weighs 18.7 tons of uranium per cubic meter (the specific gravity of iron is 7.9 tons / m ~ 3). The uranium element is chemically active and has four valences, Hexavalent two valences, is a pro-oxophilic lithophile element, so its proportion is large, does not sink into the depths of the Earth, the vast majority of “suspended” in the upper crust of the aluminum-silicon layer, in various forms (Simple oxides, complex complexes or polymorphic silicate minerals, etc.) Up to now, more than two hundred species of uranium or uranium minerals have been identified, interspersed with Uranium is a rare and precious metal in the crust of all types of rocks, and metal uranium is easily oxidized in the air and has a slightly higher temperature or even burns. Uranium has never been seen before in nature. metal.