a = 285.35 pm b = 586.97 pm c = 495.52 pm (at 20 °C)[3]
Thermal expansion
15.46×10−6/K (at 20 °C)[a]
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
Speed of sound thin rod
3155 m/s (at 20 °C)
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)
Isotopes of uranium
v
e
Main isotopes[6]
Decay
abundance
half-life (t1/2)
mode
product
232U
synth
68.9 y
α
228Th
SF
–
233U
trace
1.592×105 y[7]
α
229Th
SF
–
234U
0.005%
2.455×105 y
α
230Th
SF
–
235U
0.720%
7.04×108 y
α
231Th
SF
–
236U
trace
2.342×107 y
α
232Th
SF
–
238U
99.3%
4.468×109 y
α
234Th
SF
–
β−β−
238Pu
Category: Uranium
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Uranium is a chemical element; it has symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium radioactively decays, usually by emitting an alpha particle. The half-life of this decay varies between 159,200 and 4.5 billion years for different isotopes, making them useful for dating the age of the Earth. The most common isotopes in natural uranium are uranium-238 (which has 146 neutrons and accounts for over 99% of uranium on Earth) and uranium-235 (which has 143 neutrons). Uranium has the highest atomic 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.[8]
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 low abundance of uranium-235 in natural uranium (which is, overwhelmingly, mostly uranium-238), 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 fissile plutonium-239 in a nuclear reactor. Another fissile isotope, uranium-233, can be produced from natural thorium and is studied for future industrial use 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.[9]
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 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. Dismantling of these weapons and related nuclear facilities is carried out within various nuclear disarmament programs and costs billions of dollars. Weapon-grade uranium obtained from nuclear weapons is diluted with uranium-238 and reused as fuel for nuclear reactors. The development and deployment of these nuclear reactors continue globally as they are powerful sources of CO2-free energy. Spent nuclear fuel forms radioactive waste, which mostly consists of uranium-238 and poses a significant health threat and environmental impact.
^"Standard Atomic Weights: Uranium". CIAAW. 1999.
^Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (4 May 2022). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
^ abArblaster, John W. (2018). Selected Values of the Crystallographic Properties of Elements. Materials Park, Ohio: ASM International. ISBN 978-1-62708-155-9.
^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.
^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.
^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.
^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 6 August 2014.
^"Uranium". Encyclopaedia Britannica. Retrieved 22 April 2017.
^Emsley 2001, p. 479.
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natural uranium are uranium-238 (which has 146 neutrons and accounts for over 99% of uranium on Earth) and uranium-235 (which has 143 neutrons). Uranium has...
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