Skip to Main Content

About Uranium

Uranium Bohr

Uranium is found most commonly in the form of its various oxide minerals. Martin Heinrich Klaproth first isolated a compound of uranium from one such mineral, pitcheblende, in 1789. He subsequently named the newly discovered element after the planet Uranus. Prior to Klaproth’s discovery, pitchblende had come into use as a means for coloring glass and ceramics. Uranium glass appears either yellow or green under white light and fluoresces bright green under ultraviolet light. Products colored with uranium oxides are only negligibly radioactive and therefore are considered harmless, but the use of uranium for this purpose declined significantly as a result of demand for uranium for other uses starting during the second World War.

Uranium is the second heaviest of the naturally occurring elements, with the heaviest being plutonium. All natural isotopes of uranium are unstable, but most decay slowly, and despite the element’s association with dangerous applications of radioactivity, it is itself only weakly radioactive. In nature the element is found as uranium-238 (~99.3%) and uranium-235 (~0.7%), the latter of which can be induced to undergo nuclear fission and sustain a fission chain reaction in a nuclear reactor or nuclear weapon. Uranium is also notable for its high density--higher than lead, and surpassed by only a few elements.

Radioactivity itself was discovered through the study of uranium salts by Henri Becquerel and his colleagues Marie and Pierre Curie. The discovery of this phenomenon was made in 1896, and the trio was awarded the Nobel Prize for their discovery in 1903.The low energy radioactivity emitted from uranium under ordinary circumstances dictates that the element only presents significant hazard to life when it is brought inside the body through ingestion, inhalation, or skin absorption of contaminated materials. Uranium toxicity in these cases is caused both by low-level but persistent radiation and by the chemical toxic effects of the metal, which are similar to but milder than those caused by other heavy metals.

The most familiar use for uranium exploits the fissile nature of uranium-235 to produce massive amounts of energy, either for destruction, as in nuclear weapons, or for power generation, as in nuclear energy. Research on the possibility of sustained nuclear fission began in 1934 under the leadership of Enrico Fermi, and the first artificial self-sustained nuclear chain reaction was achieved in 1942 as part of the Manhattan project.

As only the rarer uranium isotope uranium-235, and not the more common uranium-238, can sustain fission, use of uranium for fission reactions requires an enrichment process, in which uranium isotopes in the form of uranium hexafluoride are separated by weight using high-powered centrifuges, ultimately producing uranium compounds enriched in uranium-235. Uranium may be enriched to varying degrees depending on the intended use: nuclear power plants typically use either natural uranium or uranium with less than a 20% concentration of uranium-235. Weapons grade uranium is highly enriched, containing at least 20% and often much higher concentrations uranium-235. Fast neutron reactors and naval reactors also require highly enriched uranium for operation.

Early nuclear weapons operated solely based on nuclear fission, and used highly enriched uranium as the primary fuel. Later nuclear weapon designs, known as thermonuclear weapons, used a primary fission reaction to set off a secondary fusion reaction between isotopes of hydrogen. The primary reaction may still use uranium, but more commonly uses plutonium-239, which itself is produced through the bombardment of uranium-238 with neutrons in a nuclear reactor.

The product left over following uranium enrichment is termed depleted uranium: uranium with higher lower concentrations of the fissile uranium-235 than are typically found in nature. Depleted uranium metal is used widely in military applications as both armor and munitions, both applications that benefit from the high density of the material. In civilian applications, depleted uranium is used primarily for shielding from high-energy radiation sources, such as the iridium-192 used in industrial radiography. Compound forms of depleted uranium are often used in laboratory settings, most often in stains for use in electron microscopy.

Uranium is obtained commercially from the extraction and processing of uranium-bearing minerals such as uraninite. The ores are processed through grinding to a uniform particle size and then treating with acid to chemically leach the uranium from the ore. The material ultimately produced by this process is the standard form of natural uranium sold on the market, a powdered form of uranium oxide known as “yellowcake”. Where enriched uranium is required, yellowcake is treated with various chemicals to produce uranium hexafluoride, known as “hex” in the nuclear industry. Uranium hexafluoride is highly toxic and reactive, and because it is corrosive to most metals is hazardous to store, but is the primary raw material for all uranium enrichment techniques.

High Purity (99.999%) Uranium Oxide (UO) Powder Uranium in its depleted and unenriched forms has numerous commercial applications due to its great density and its bright yellow-green color in glass and ceramics. Because of its great density it has found military applications in armor piercing armaments and in protective shielding. Uranyl nitrate and uranyl acetate are used in medical and analytical laboratories.

Uranium Properties

Uranium Bohr ModelUranium is a Block F, Group 3, Period 7 element. The number of electrons in each of Uranium's shells is 2, 8, 18, 32, 21, 9, 2 and its electron configuration is [Rn] 5f3 6d1 7s2. The uranium atom has a radius of and its Van der Waals radius is In its elemental form, CAS 7440-61-1, uranium has a silvery gray metallic appearance. Uranium was discovered by Martin Heinrich Klaproth in 1789. It was first isolated by Eugène-Melchior Péligot in 1841. The name Uranium originates from the planet Uranus.

Uranium information, including technical data, properties, and other useful facts are specified below. Scientific facts such as the atomic structure, ionization energy, abundance on Earth, conductivity, and thermal properties are included.

Symbol: U
Atomic Number: 92
Atomic Weight: 238
Element Category: Actinide
Group, Period, Block: n/a, 7, f
Color: metallic gray/ silvery-white
Other Names: D'uranium, Uran, Uranio
Melting Point: 1135°C, 2075°F, 1408.15 K
Boiling Point: 4131°C, 7467.8°F, 4404.15 K
Density: 19050 kg·m3
Liquid Density @ Melting Point: 17.3 g·cm3
Density @ 20°C: 18.9 g/cm3
Density of Solid: 19050 kg·m3
Specific Heat: N/A
Superconductivity Temperature: 0.2 [or -272.9 °C (-459.2 °F)] K
Triple Point: N/A
Critical Point: N/A
Heat of Fusion (kJ·mol-1): 15.5
Heat of Vaporization (kJ·mol-1): 417.1
Heat of Atomization (kJ·mol-1): 535.43
Thermal Conductivity: 27.5 W·m-1·K-1
Thermal Expansion: (25 °C) 13.9 µm·m-1·K-1
Electrical Resistivity: (0 °C) 0.280 µΩ·m
Tensile Strength: N/A
Molar Heat Capacity: 27.665 J·mol-1·K-1
Young's Modulus: 208 GPa
Shear Modulus: 111 GPa
Bulk Modulus: 100 GPa
Poisson Ratio: 0.23
Mohs Hardness: N/A
Vickers Hardness: N/A
Brinell Hardness: N/A
Speed of Sound: (20 °C) 3155 m·s-1
Pauling Electronegativity: 1.38
Sanderson Electronegativity: N/A
Allred Rochow Electronegativity: 1.22
Mulliken-Jaffe Electronegativity: N/A
Allen Electronegativity: N/A
Pauling Electropositivity: 2.62
Reflectivity (%): N/A
Refractive Index: N/A
Electrons: 92
Protons: 92
Neutrons: 146
Electron Configuration: [Rn] 5f3 6d1 7s2
Atomic Radius: 156 pm
Atomic Radius,
non-bonded (Å):
Covalent Radius: 196±7 pm
Covalent Radius (Å): 1.83
Van der Waals Radius: 186 pm
Oxidation States: 6, 5, 4
Phase: Solid 
Crystal Structure: orthorhombic
Magnetic Ordering: paramagnetic
Electron Affinity (kJ·mol-1) Unknown
1st Ionization Energy: 597.6 kJ·mol-1
2nd Ionization Energy: 1420 kJ·mol-1
3rd Ionization Energy: N/A
CAS Number: 7440-61-1
EC Number: N/A
MDL Number: N/A
Beilstein Number: N/A
SMILES Identifier: [U]
InChI Identifier: InChI=1S/U
PubChem CID: 23989
ChemSpider ID: 22425
Earth - Total: 14.3 ppb
Mercury - Total:  11.0 ppb
Venus - Total: 15.0 ppb 
Earth - Seawater (Oceans), ppb by weight: 3.3
Earth - Seawater (Oceans), ppb by atoms: 0.086
Earth -  Crust (Crustal Rocks), ppb by weight: 1800
Earth -  Crust (Crustal Rocks), ppb by atoms: 150
Sun - Total, ppb by weight: 1
Sun - Total, ppb by atoms: 0.004
Stream, ppb by weight: 0.04
Stream, ppb by atoms: 0.0002
Meterorite (Carbonaceous), ppb by weight: 10
Meterorite (Carbonaceous), ppb by atoms: 1
Typical Human Body, ppb by weight: N/A
Typical Human Body, ppb by atom: N/A
Universe, ppb by weight: N/A
Universe, ppb by atom: N/A
Discovered By: Martin Heinrich Klaproth
Discovery Date: 1789
First Isolation: Eugène-Melchior Péligot (1841)

Health, Safety & Transportation Information for Uranium

Uranium is harmful both through its radioactive nature and its chemical toxicity. The below information applies to elemental (metallic) Uranium.

Safety Data
Material Safety Data Sheet MSDS
Signal Word Warning
Hazard Statements H315-H319
Hazard Codes Xi
Risk Codes 36-38
Safety Precautions 26
RTECS Number N/A
Transport Information N/A
WGK Germany 1
Globally Harmonized System of
Classification and Labelling (GHS)
Exclamation Mark-Acute Toxicity

Uranium Isotopes

Uranium has two primordial isotopes with long half-lives: 235U and 238U. Both of these are found in the earth's crust. It has no stable isotopes.

Nuclide Isotopic Mass Half-Life Mode of Decay Nuclear Spin Magnetic Moment Binding Energy (MeV) Natural Abundance
(% by atom)
217U 217.02437(9) 26(14) ms [16(+21-6) ms] Unknown 1/2-# N/A 1631.22 -
218U 218.02354(3) 6(5) ms α to 214Th 0+ N/A 1639.3 -
219U 219.02492(6) 55(25) µs [42(+34-13) µs] α to 215Th 9/2+# N/A 1647.37 -
220U 220.02472(22)# 60# ns α to 216Th 0+ N/A 1655.45 -
221U 221.02640(11)# 700# ns α to 217Th 9/2+# N/A 1663.53 -
222U 222.02609(11)# 1.4(7) µs [1.0(+10-4) µs] α to 218Th; β+ to 222Pa 0+ N/A 1671.61 -
223U 223.02774(8) 21(8) µs [18(+10-5) µs] α to 219Th 7/2+# N/A 1679.69 -
224U 224.027605(27) 940(270) µs α to 220Th 0+ N/A 1687.77 -
225U 225.02939# 61(4) ms α to 221Th (5/2+)# N/A 1695.85 -
226U 226.029339(14) 269(6) ms α to 222Th 0+ N/A 1703.93 -
227U 227.031156(18) 1.1(1) min α to 223Th; β+ to 227Pa (3/2+) N/A 1702.69 -
228U 228.031374(16) 9.1(2) min α to 224Th; EC 0+ N/A 1710.77 -
229U 229.033506(6) 58(3) min β+ to 229Pa; α to 225Th (3/2+) N/A 1718.85 -
230U 230.033940(5) 20.8 d α to 226Th 0+ N/A 1726.92 -
231U 231.036294(3) 4.2(1) d α to 227Th (5/2)(+#) N/A 1735 -
232U 232.0371562(24) 68.9(4) y α to 228Th 0+ N/A 1743.08 -
233U 233.0396352(29) 1.592(2)x105 y α to 229Th; SF 5/2+ 0.59 1751.16 -
234U 234.0409521(20) 2.455(6)x105 y α to 230Th; SF 0+ 0 1749.92 [0.0055 ]
235U 235.0439299(20) 7.04(1)x108 y α to 231Th; SF 7/2- 0.38/-0.35 1758 [0.7200 ]
236U 236.045568(2) 2.342(3)x107 y α to 232Th; SF 0+ N/A 1766.08 -
237U 237.0487302(20) 6.75(1) d β- to 237Np 1/2+ N/A 1774.16 -
238U 238.0507882(20) 4.468(3)x109 y α to 234Th; SF; 2β- to 238Pu 0+ 0 1772.92 [99.2745 ]
239U 239.0542933(21) 23.45(2) min β- to 239Np 5/2+ N/A 1781 -
240U 240.056592(6) 14.1(1) h β- to 240Np; α to 236Th 0+ N/A 1789.08 -
241U 241.06033(32)# 5# min β- to 241Np 7/2+# N/A 1787.84 -
242U 242.06293(22)# 16.8(5) min β- to 242Np 0+ N/A 1795.92 -
Uranium Elemental Symbol

Recent Research & Development for Uranium

  • The [U2(μ-S2)2Cl8](4-) Anion: Synthesis and Characterization of the Uranium Double Salt Cs5[U2(μ-S2)2Cl8]I. Ward MD, Pozzi EA, Lee M, Van Duyne RP, Choi ES, Ibers JA. Inorg Chem. 2015 Mar 16
  • Uranium transport in a crushed granodiorite: Experiments and reactive transport modeling. Dittrich TM, Reimus PW. J Contam Hydrol. 2015 Feb 12
  • Cellular localization of uranium in the renal proximal tubules during acute renal uranium toxicity. Homma-Takeda S, Kitahara K, Suzuki K, Blyth BJ, Suya N, Konishi T, Terada Y, Shimada Y. J Appl Toxicol. 2015 Mar 13.
  • XAS and TRLIF spectroscopy of uranium and neptunium in seawater. Maloubier M, Solari PL, Moisy P, Monfort M, Den Auwer C, Moulin C. Dalton Trans. 2015 Mar 10
  • Oxygen transport in off-stoichiometric uranium dioxide mediated by defect clustering dynamics. Yu J, Bai XM, El-Azab A, Allen TR. J Chem Phys. 2015 Mar 7
  • Efficient removal of uranium from aqueous solution by zero-valent iron nanoparticle and its graphene composite. Li ZJ, Wang L, Yuan LY, Xiao CL, Mei L, Zheng LR, Zhang J, Yang JH, Zhao YL, Zhu ZT, Chai ZF, Shi WQ. J Hazard Mater. 2015 Feb 11
  • In situ characterization of uranium and americium oxide solid solution formation for CRMP process: first combination of in situ XRD and XANES measurements. Caisso M, Picart S, Belin RC, Lebreton F, Martin PM, Dardenne K, Rothe J, Neuville DR, Delahaye T, Ayral A. Dalton Trans. 2015 Mar 6.
  • Multiple inorganic toxic substances contaminating the groundwater of Myingyan Township, Myanmar: Arsenic, manganese, fluoride, iron, and uranium. Bacquart T, Frisbie S, Mitchell E, Grigg L, Cole C, Small C, Sarkar B. Sci Total Environ. 2015 Mar 4
  • Preparation of magnetic core-shell iron oxide@silica@nickel-ethylene glycol microspheres for highly efficient sorption of uranium(vi). Tan L, Zhang X, Liu Q, Wang J, Sun Y, Jing X, Liu J, Song D, Liu L. Dalton Trans. 2015 Mar 16.
  • Uranium modifies or not behavior and antioxidant status in the hippocampus of rats exposed since birth. Lestaevel P, Dhieux B, Delissen O, Benderitter M, Aigueperse J. J Toxicol Sci. 2015 Feb
  • Ligand-exchange mechanism: new insight into solid-phase extraction of uranium based on a combined experimental and theoretical study. Tian Y, Fu J, Zhang Y, Cao K, Bai C, Wang D, Li S, Xue Y, Ma L, Zheng C. Phys Chem Chem Phys. 2015 Mar 4
  • Enrichment and encapsulation of uranium with iron nanoparticle. Ling L, Zhang WX. J Am Chem Soc. 2015 Mar 4
  • Fluorescence Quenching Determination of Uranium (VI) Binding Properties by Two Functional Proteins: Acetylcholinesterase (AChE) and Vitellogenin (Vtg). Coppin F, Michon J, Garnier C, Frelon S. J Fluoresc. 2015 Mar 13.
  • Levels of rare earth elements, heavy metals and uranium in a population living in Baiyun Obo, Inner Mongolia, China: A pilot study. Hao Z, Li Y, Li H, Wei B, Liao X, Liang T, Yu J. Chemosphere. 2015 Feb 19
  • Positional Flexibility: Syntheses and Characterization of Six Uranium Chalcogenides Related to the 2H Hexagonal Perovskite Family. Mesbah A, Prakash J, Beard JC, Pozzi EA, Tarasenko MS, Lebègue S, Malliakas CD, Van Duyne RP, Ibers JA. Inorg Chem. 2015 Mar 16
  • Crystal structure of dioxidobis(pentane-2,4-dionato-k(2) O,O')[1-phenyl-3-(pyridin-4-yl)propane-kN]uranium(VI). Kawasaki T, Kitazawa T. Acta Crystallogr E Crystallogr Commun. 2015 Jan 1
  • High-Quality Draft Genome Sequence of Desulfovibrio carbinoliphilus FW-101-2B, an Organic Acid-Oxidizing Sulfate-Reducing Bacterium Isolated from Uranium(VI)-Contaminated Groundwater. Ramsay BD, Hwang C, Woo HL, Carroll SL, Lucas S, Han J, Lapidus AL, Cheng JF, Goodwin LA, Pitluck S, Peters L, Chertkov O, Held B, Detter JC, Han CS, Tapia R, Land ML, Hauser LJ, Kyrpides NC, Ivanova NN, Mikhailova N, Pagani I, Woyke T, Arkin AP, Dehal P, Chivian D, Criddle CS, Wu W, Chakraborty R, Hazen TC, Fields MW. Genome Announc. 2015 Mar 12
  • Speciation of uranium in compartments of living cells. Geipel G, Viehweger K. Biometals. 2015 Feb 28.
  • Efficient Uranium Capture by Polysulfide/Layered Double Hydroxide Composites. Ma S, Huang L, Ma L, Shim Y, Islam SM, Wang P, Zhao LD, Wang S, Sun G, Yang X, Kanatzidis MG. J Am Chem Soc. 2015 Mar 10.
  • The use of unmanned aerial systems for the mapping of legacy uranium mines. Martin PG, Payton OD, Fardoulis JS, Richards DA, Scott TB. J Environ Radioact. 2015 Mar 11