Uranium is a chemical compound.
Uranium is a chemical element with symbol U and atomic number 92 .. chemical element. chemical element. atomic number. atomic number. It is a silvery-white metal in the actinide series of the periodic table .. metal. metal. actinide. actinide. periodic table. periodic table. A uranium atom has 92 protons and 92 electrons , of which 6 are valence electrons .. Uranium is weakly radioactive because all its isotopes are unstable -LRB- with half-lives of the six naturally known isotopes , uranium-233 to uranium-238 , varying between 69 years and 4.5 billion years -RRB- .. radioactive. radioactive decay. uranium-238. uranium-238. billion. 1000000000 ( number ). uranium-233. uranium-233. The most common isotopes in natural uranium are uranium-238 -LRB- which has 146 neutrons and accounts for over 99 % -RRB- and uranium-235 -LRB- which has 143 neutrons -RRB- .. natural uranium. natural uranium. uranium-238. uranium-238. uranium-235. uranium-235. Uranium has the highest atomic weight of the primordially occurring elements .. atomic weight. atomic weight. primordially. primordial nuclide. Its density is about 70 % higher than that of lead , and slightly lower than that of gold or tungsten .. density. density. lead. lead. gold. gold. tungsten. tungsten. It occurs naturally in low concentrations of a few parts per million in soil , rock and water , and is commercially extracted from uranium-bearing minerals such as uraninite .. parts per million. Parts-per notation#Parts-per expressions. extracted. uranium mining. uraninite. uraninite. million. million. In nature , uranium is found as uranium-238 -LRB- 99.2739 -- 99.2752 % -RRB- , uranium-235 -LRB- 0.7198 -- 0.7202 % -RRB- , and a very small amount of uranium-234 -LRB- 0.0050 -- 0.0059 % -RRB- .. uranium-238. uranium-238. uranium-235. uranium-235. uranium-234. uranium-234. Uranium decays slowly by emitting an alpha particle .. alpha particle. alpha particle. The half-life of uranium-238 is about 4.47 billion years and that of uranium-235 is 704 million years , making them useful in dating the age of the Earth .. uranium-238. uranium-238. uranium-235. uranium-235. half-life. half-life. billion. 1000000000 ( number ). million. million. age of the Earth. age of the Earth. Many contemporary uses of uranium exploit its unique nuclear properties .. nuclear. atomic nucleus. Uranium-235 is the only naturally occurring fissile isotope , which makes it widely used in nuclear power plants and nuclear weapons .. isotope. isotope. nuclear. atomic nucleus. fissile. fissile. However , because of the tiny amounts found in nature , uranium needs to undergo enrichment so that enough uranium-235 is present .. uranium-235. uranium-235. enrichment. uranium enrichment. Uranium-238 is fissionable by fast neutrons , and is fertile , meaning it can be transmuted to fissile plutonium-239 in a nuclear reactor .. nuclear. atomic nucleus. fissile. fissile. transmuted. Nuclear transmutation. plutonium-239. plutonium-239. nuclear reactor. nuclear reactor. Another fissile isotope , uranium-233 , can be produced from natural thorium and is also important in nuclear technology .. isotope. isotope. nuclear. atomic nucleus. fissile. fissile. uranium-233. uranium-233. thorium. thorium. Uranium-238 has a small probability for spontaneous fission or even induced fission with fast neutrons ; uranium-235 and to a lesser degree uranium-233 have a much higher fission cross-section for slow neutrons .. uranium-235. uranium-235. uranium-233. uranium-233. spontaneous fission. spontaneous fission. In sufficient concentration , these isotopes maintain a sustained nuclear chain reaction .. nuclear. atomic nucleus. nuclear chain reaction. nuclear chain reaction. This generates the heat in nuclear power reactors , and produces the fissile material for nuclear weapons .. nuclear. atomic nucleus. fissile. fissile. Depleted uranium -LRB- 238U -RRB- is used in kinetic energy penetrators and armor plating .. Depleted uranium. Depleted uranium. armor plating. vehicle armour. Uranium is used as a colorant in uranium glass , producing lemon yellow to green colors .. uranium glass. uranium glass. Uranium glass fluoresces green in ultraviolet light .. It was also used for tinting and shading in early photography .. photography. photography. The 1789 discovery of uranium in the mineral pitchblende is credited to Martin Heinrich Klaproth , who named the new element after the planet Uranus .. mineral. mineral. discovery. discovery of the chemical elements. pitchblende. uraninite. Martin Heinrich Klaproth. Martin Heinrich Klaproth. Uranus. Uranus. Eugene-Melchior Peligot was the first person to isolate the metal and its radioactive properties were discovered in 1896 by Henri Becquerel .. metal. metal. radioactive. radioactive decay. Eugene-Melchior Peligot. Eugene-Melchior Peligot. Henri Becquerel. Henri Becquerel. Research by Otto Hahn , Lise Meitner , Enrico Fermi and others , such as J. Robert Oppenheimer starting in 1934 led to its use as a fuel in the nuclear power industry and in Little Boy , the first nuclear weapon used in war .. nuclear. atomic nucleus. nuclear weapon. nuclear weapon. Otto Hahn. Otto Hahn. Lise Meitner. Lise Meitner. Enrico Fermi. Enrico Fermi. J. Robert Oppenheimer. J. Robert Oppenheimer. Little Boy. Little Boy. first nuclear weapon used in war. Atomic bombings of Hiroshima and Nagasaki. An ensuing arms race during the Cold War between the United States and the Soviet Union produced tens of thousands of nuclear weapons that used uranium metal and uranium-derived plutonium-239 .. metal. metal. nuclear. atomic nucleus. plutonium-239. plutonium-239. arms race. arms race. Cold War. Cold War. United States. United States. Soviet Union. Soviet Union. The security of those weapons and their fissile material following the breakup of the Soviet Union in 1991 is an ongoing concern for public health and safety .. fissile. fissile. Soviet Union. Soviet Union. breakup of the Soviet Union. Collapse of the Soviet Union ( 1985–1991 )#Dissolution of the USSR. See Nuclear proliferation .. Nuclear proliferation. Nuclear proliferation