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Uranium, 00U
Two hands in brown gloves holding a blotched gray disk with a number 2068 hand-written on it
Pronunciation/jʊˈrniəm/ (yuu-RAY-nee-əm)
Appearancesilvery gray metallic; corrodes to a spalling black oxide coat in air
Standard atomic weight Ar°(U)
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


Groupf-block groups (no number)
Periodperiod 7
Block  f-block
Electron configuration[Rn] 5f3 6d1 7s2
Electrons per shell2, 8, 18, 32, 21, 9, 2
Physical properties
Phase at STPsolid
Melting point1405.3 K ​(1132.2 °C, ​2070 °F)
Boiling point4404 K ​(4131 °C, ​7468 °F)
Density (near r.t.)19.1 g/cm3
when liquid (at m.p.)17.3 g/cm3
Heat of fusion9.14 kJ/mol
Heat of vaporization417.1 kJ/mol
Molar heat capacity27.665 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−1,[2] +1, +2, +3,[3] +4, +5, +6 (an amphoteric oxide)
ElectronegativityPauling scale: 1.38
Ionization energies
  • 1st: 597.6 kJ/mol
  • 2nd: 1420 kJ/mol
Atomic radiusempirical: 156 pm
Covalent radius196±7 pm
Van der Waals radius186 pm
Color lines in a spectral range
Spectral lines of uranium
Other properties
Natural occurrenceprimordial
Crystal structureorthorhombic
Orthorhombic crystal structure for uranium
Speed of sound thin rod3155 m/s (at 20 °C)
Thermal expansion13.9 µm/(m⋅K) (at 25 °C)
Thermal conductivity27.5 W/(m⋅K)
Electrical resistivity0.280 µΩ⋅m (at 0 °C)
Magnetic orderingparamagnetic
Young's modulus208 GPa
Shear modulus111 GPa
Bulk modulus100 GPa
Poisson ratio0.23
Vickers hardness1960–2500 MPa
Brinell hardness2350–3850 MPa
CAS Number7440-61-1
Namingafter planet Uranus, itself named after Greek god of the sky Uranus
DiscoveryMartin Heinrich Klaproth (1789)
First isolationEugène-Melchior Péligot (1841)
Isotopes of uranium
Main isotopes[4] Decay
abun­dance half-life (t1/2) mode pro­duct
232U synth 68.9 y α 228Th
233U trace 1.592×105 y[5] α 229Th
234U 0.005% 2.455×105 y α 230Th
235U 0.720% 7.04×108 y α 231Th
236U trace 2.342×107 y α 232Th
238U 99.3% 4.468×109 y α 234Th
ββ 238Pu
 Category: Uranium
| references
A small amount of uranium in a glass dish

Uranium is a chemical element (a metal) on the periodic table. It has an atomic number of 92, which means that a uranium atom has 92 protons in its center, the nucleus.

Uranium dug out of the ground is made from three different isotopes. The isotopes are different types of uranium with different numbers of neutrons in their nuclei. Most of it is uranium-238; uranium-235 is less common; uranium-234 is the rarest. Pitchblende is the main ore that is mined for uranium.

Uranium-235 can be used in nuclear reactors and nuclear weapons by making a nuclear chain reaction. This turns the uranium-235 into uranium-236 and splits the nucleus into two smaller nuclei. This makes two completely different elements with smaller atomic numbers. The process is called nuclear fission and creates lots of heat. This heat makes it very useful for making steam in nuclear reactors, or for making explosions with nuclear weapons. Most such weapons use plutonium made from uranium-238. Uranium is slightly radioactive.

Uranium without its uranium-235 is called depleted uranium. It is less radioactive than natural uranium. It is used in anti-tank weapons. Uranium can also be used as a dye for stained glass or pottery.

A trefoil radiation warning

Uranium is a dangerous substance. Because uranium is radioactive it is often seen with the hazard sign for radioactive elements, a group of three triangles with curved outer edges pointing in towards the middle (as you can see on the left). Uranium is a shiny white metal, but is usually seen in its oxide form which is black. Spent or partially spent uranium fuel rods are kept underwater, inside a nuclear reactor or in a spent fuel pool. Uranium can glow blue due to Cherenkov radiation. In addition to being radioactive, uranium is a heavy metal and is chemically toxic.

Characteristics[change | change source]

Uranium is a silvery white, weakly radioactive metal. It has a Mohs hardness of 6. It is malleable, ductile and slightly paramagnetic. It is strongly electropositive. It is a poor electrical conductor.[7][8] Uranium metal has a very high density of 19.1 g/cm3.[9]

Uranium metal reacts with almost all non-metal elements and their compounds. Hydrochloric and nitric acids dissolve uranium, but non-oxidizing acids other than hydrochloric acid dissolve the element very slowly.[7]

Uranium-235 was the first isotope that was found to be fissile: The molecule splits. Other naturally occurring isotopes are fissionable (can be broken down), but are not fissile.

As little as 15 lb (7 kg) of uranium-235 can be used to make an atomic bomb. The nuclear weapon detonated over Hiroshima, called Little Boy, relied on uranium fission.

History[change | change source]

Pre-discovery use[change | change source]

The planet Uranus, which uranium is named after

The use of uranium in its natural oxide form dates back to the year 79 AD. It was used in the Roman Empire to make ceramic glazes yellow.[8] Yellow glass with 1% uranium oxide was found in a Roman villa on Cape Posillipo in the Bay of Naples, Italy. It was found by R.T. Gunther of the University of Oxford in 1912. In the late Middle Ages, pitchblende was extracted from the Habsburg silver mines in Joachimsthal, Bohemia (now Jáchymov in the Czech Republic). In the early 19th century, the world's only known sources of uranium ore were these mines.

Origin[change | change source]

Uranium is only naturally formed by the rapid neutron capture in supernovae and neutron star mergers.[10][11][12]

Radioactive heat production is present on Earth in quantities. It may be a widespread component of Solar System planets, and possible other planetary systems. That might help to explain the high internal temperatures of planets.

Mining[change | change source]

The world's largest producer of uranium is Kazakhstan, which in 2019 produced 43% of the world's mining output. Canada was the next largest producer with a 13% share, followed by Australia with 12%.[13] Uranium has been mined in every continent except Antarctica.

References[change | change source]

  1. "Standard Atomic Weights: Uranium". CIAAW. 1999.
  2. Th(-I) and U(-I) have been detected in the gas phase as octacarbonyl anions; see Chaoxian, Chi; Sudip, Pan; Jiaye, Jin; Luyan, Meng; Mingbiao, Luo; Lili, Zhao; Mingfei, Zhou; Gernot, Frenking (2019). "Octacarbonyl Ion Complexes of Actinides [An(CO)8]+/− (An=Th, U) and the Role of f Orbitals in Metal–Ligand Bonding". Chemistry (Weinheim an der Bergstrasse, Germany). 25 (50): 11772–11784. 25 (50): 11772–11784. doi:10.1002/chem.201902625. ISSN 0947-6539. PMC 6772027. PMID 31276242.
  3. Morss, L.R.; Edelstein, N.M.; Fuger, J., eds. (2006). The Chemistry of the Actinide and Transactinide Elements (3rd ed.). Netherlands: Springer. ISBN 978-9048131464.
  4. Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
  5. Magurno, B.A.; Pearlstein, S, eds. (1981). Proceedings of the conference on nuclear data evaluation methods and procedures. BNL-NCS 51363, vol. II (PDF). Upton, NY (USA): Brookhaven National Lab. pp. 835 ff. Retrieved 2014-08-06.
  6. Morss, L.R.; Edelstein, N.M.; Fuger, J., eds. (2006). The Chemistry of the Actinide and Transactinide Elements (3rd ed.). Netherlands: Springer. ISBN 9048131464.
  7. 7.0 7.1 McGraw-Hill concise encyclopedia of science & technology (5th ed.). New York: McGraw-Hill. 2005. ISBN 0-07-142957-3. OCLC 56198760.
  8. 8.0 8.1 CRC handbook of chemistry and physics, 2000-2001. Lide, David R., 1928- (81st ed.). Boca Raton: CRC Press. 2000. ISBN 0-8493-0481-4. OCLC 44440496.{{cite book}}: CS1 maint: others (link)
  9. "Uranium - Element information, properties and uses | Periodic Table". www.rsc.org. Retrieved 2020-11-20.
  10. "History/Origin of Chemicals". NASA. Retrieved 1 January 2013.
  11. Burbidge E.M.; Burbidge G.R.; Fowler W.A.; Hoyle F. 1957. Synthesis of the elements in stars. Reviews of Modern Physics 29 (4): 547. Bibcode:1957RvMP...29..547B. doi:10.1103/RevModPhys.29.547.
  12. Clayton, Donald D. 1968. Principles of stellar evolution and nucleosynthesis. New York: Mc-Graw-Hill. pp. 577–91. ISBN 978-0226109534
  13. "Uranium Production Figures, 2009-2018". London: World Nuclear Association. August 2019. Retrieved 19 March 2020.

See also: Uranium mining