Uranium is a chemical element with symbol U and atomic number 92.

Uranium  {Uranium,  ₉₂U  ..............................................................................................................................................

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Uranium,  ₉₂U

Uranium is a chemical element with symbol U and atomic number 92. It is a silvery-white metal in the actinideseries of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weakly radioactive because all isotopes of uranium are unstable, with half-lives varying between 159,200 years and 4.5 billion years. The most common isotopes in natural uranium are uranium-238 (which has 146 neutrons and accounts for over 99%) and uranium-235 (which has 143 neutrons). Uranium has the highestatomic weight of the primordially occurring elements. Its density is about 70% higher than that of lead, and slightly lower than that of gold or 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.^[3]

In nature, uranium is found as uranium-238 (99.2739–99.2752%), uranium-235 (0.7198–0.7202%), and a very small amount of uranium-234 (0.0050–0.0059%).^[4] Uranium decays slowly by emitting an alpha particle. The half-life of uranium-238 is about 4.47 billion years and that of uranium-235 is 704 million years,^[5] making them useful in dating the age of the Earth.

Many contemporary uses of uranium exploit its unique nuclear properties. Uranium-235 is the only naturally occurring fissile isotope, which makes it widely used in nuclear power plants and nuclear weapons. However, because of the tiny amounts found in nature, uranium needs to undergo enrichment so that enough uranium-235 is present. Uranium-238 is fissionable by fast neutrons, and is fertile, meaning it can be transmuted to fissileplutonium-239 in a nuclear reactor. Another fissile isotope, uranium-233, can be produced from natural thoriumand is also important in nuclear technology. 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. In sufficient concentration, these isotopes maintain a sustained nuclear chain reaction. This generates the heat in nuclear power reactors, and produces the fissile material for nuclear weapons.Depleted uranium (²³⁸U) is used in kinetic energy penetrators and armor plating.^[6] Uranium is used as a colorant inuranium glass, producing lemon yellow to green colors. Uranium glass fluoresces green in ultraviolet light. It was also used for tinting and shading in early photography.

The 1789 discovery of uranium in the mineral pitchblende is credited to Martin Heinrich Klaproth, who named the new element after the recently-discovered planet Uranus. Eugène-Melchior Péligot was the first person to isolate the metal and its radioactive properties were discovered in 1896 by 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. An ensuing arms race during theCold 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. 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.^[7] See Nuclear proliferation.

General properties
Pronunciation	/jʊəˈreɪniəm/ ​(yoor-AY-nee-əm)
Appearance	silvery gray metallic; corrodes to a spalling black oxide coat in air
Standard atomic weight (Ar, standard)	238.02891(3)[1]
Uranium in the periodic table
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson Nd ↑ U ↓ (Uqh) protactinium ← uranium → neptunium
Atomic number (Z)	92
Group	group n/a
Period	period 7
Element category	actinide
Block	f-block
Electron configuration	[Rn] 5f3 6d1 7s2
Electrons per shell	2, 8, 18, 32, 21, 9, 2
Physical properties
Phase at STP	solid
Melting point	1405.3 K ​(1132.2 °C, ​2070 °F)
Boiling point	4404 K ​(4131 °C, ​7468 °F)
Density (near r.t.)	19.1 g/cm3
when liquid (at m.p.)	17.3 g/cm3
Heat of fusion	9.14 kJ/mol
Heat of vaporization	417.1 kJ/mol
Molar heat capacity	27.665 J/(mol·K)
Vapor pressure P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 2325 2564 2859 3234 3727 4402
Atomic properties
Oxidation states	6, 5, 4, 3,[2] 2, 1 ​(a weaklybasic oxide)
Electronegativity	Pauling scale: 1.38
Ionization energies	1st: 597.6 kJ/mol 2nd: 1420 kJ/mol
Atomic radius	empirical: 156 pm
Covalent radius	196±7 pm
Van der Waals radius	186 pm
Spectral lines
Miscellanea
Crystal structure	​orthorhombic
Speed of soundthin rod	3155 m/s (at 20 °C)
Thermal expansion	13.9 µm/(m·K) (at 25 °C)
Thermal conductivity	27.5 W/(m·K)
Electrical resistivity	0.280 µΩ·m (at 0 °C)
Magnetic ordering	paramagnetic
Young's modulus	208 GPa
Shear modulus	111 GPa
Bulk modulus	100 GPa
Poisson ratio	0.23
Vickers hardness	1960–2500 MPa
Brinell hardness	2350–3850 MPa
CAS Number	7440-61-1
History
Naming	after planet Uranus, itself named after Greek god of the sky Uranus
Discovery	Martin Heinrich Klaproth(1789)
First isolation	Eugène-Melchior Péligot(1841)
Main isotopes of uranium
Iso­tope Abun­dance Half-life(t1/2) Decay mode Pro­duct 232U syn 68.9 y SF – α 228Th 233U trace 1.592×105 y SF – α 229Th 234U 0.005% 2.455×105 y SF – α 230Th 235U 0.720% 7.04×108 y SF – α 231Th 236U trace 2.342×107 y SF – α 232Th 238U 99.274% 4.468×109 y α 234Th SF – β−β− 238Pu