Thorium is a chemical element. It has the symbol Th and atomic number 90. Thorium is a weakly radioactive light silver metal which tarnishes olive gray when it is exposed to air, forming thorium dioxide; it is moderately soft and malleable and has a high melting point. Thorium is an electropositive actinide whose chemistry is dominated by the +4 oxidation state; it is quite reactive and can ignite in air when finely divided.
All known thorium isotopes are unstable. The most stable isotope, 232Th, has a half-life of 14.05 billion years, or about the age of the universe; it decays very slowly via alpha decay, starting a decay chain named the thorium series that ends at stable 208Pb. On Earth, thorium and uranium are the only elements with no stable or nearly-stable isotopes that still occur naturally in large quantities as primordial elements.[a] Thorium is estimated to be over three times as abundant as uranium in the Earth's crust, and is chiefly refined from monazite sands as a by-product of extracting rare-earth metals.
Thorium was discovered in 1828 by the Norwegian amateur mineralogist Morten Thrane Esmark and identified by the Swedish chemist Jöns Jacob Berzelius, who named it after Thor, the Norse god of thunder. Its first applications were developed in the late 19th century. Thorium's radioactivity was widely acknowledged during the first decades of the 20th century. In the second half of the century, thorium was replaced in many uses due to concerns about its radioactivity.
Thorium is still being used as an alloying element in TIG welding electrodes but is slowly being replaced in the field with different compositions. It was also material in high-end optics and scientific instrumentation, used in some broadcast vacuum tubes, and as the light source in gas mantles, but these uses have become marginal. It has been suggested as a replacement for uranium as nuclear fuel in nuclear reactors, and several thorium reactors have been built. Thorium is also used in strengthening magnesium, coating tungsten wire in electrical equipment, controlling the grain size of tungsten in electric lamps, high-temperature crucibles, and glasses including camera and scientific instrument lenses. Other uses for thorium include heat-resistant ceramics, aircraft engines, and in light bulbs. Ocean science has utilised 231Pa/230Th isotope ratios to understand the ancient ocean.[9]
^"Standard Atomic Weights: Thorium". CIAAW. 2013.
^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.
^ abcArblaster, 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.
^Lide, D. R., ed. (2005). "Magnetic susceptibility of the elements and inorganic compounds". CRC Handbook of Chemistry and Physics(PDF) (86th ed.). CRC Press. pp. 4–135. ISBN 978-0-8493-0486-6.
^Weast, R. (1984). CRC, Handbook of Chemistry and Physics. Chemical Rubber Company Publishing. p. E110. ISBN 978-0-8493-0464-4.
^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.
^Varga, Z.; Nicholl, A.; Mayer, K. (2014). "Determination of the 229Th half-life". Physical Review C. 89 (6): 064310. doi:10.1103/PhysRevC.89.064310.
^Negre, César et al. “Reversed flow of Atlantic deep water during the Last Glacial Maximum.” Nature, vol. 468,7320 (2010): 84-8. doi:10.1038/nature09508
Cite error: There are <ref group=lower-alpha> tags or {{efn}} templates on this page, but the references will not show without a {{reflist|group=lower-alpha}} template or {{notelist}} template (see the help page).
Thorium is a chemical element. It has the symbol Th and atomic number 90. Thorium is a weakly radioactive light silver metal which tarnishes olive gray...
Thorium (90Th) has seven naturally occurring isotopes but none are stable. One isotope, 232Th, is relatively stable, with a half-life of 1.405×1010 years...
The thorium fuel cycle is a nuclear fuel cycle that uses an isotope of thorium, 232 Th , as the fertile material. In the reactor, 232 Th is transmuted...
Thorium dioxide (ThO2), also called thorium(IV) oxide, is a crystalline solid, often white or yellow in colour. Also known as thoria, it is mainly a by-product...
Thorium oxyfluoride is an inorganic compound of thorium metal, fluorine, and oxygen with the chemical formula ThOF 2. Thorium oxyfluoride can be prepared...
isotope. One example of this is uranium (atomic number 92) decaying into thorium (atomic number 90). The daughter isotope may be stable or it may decay...
The liquid fluoride thorium reactor (LFTR; often pronounced lifter) is a type of molten salt reactor. LFTRs use the thorium fuel cycle with a fluoride-based...
Thorium is found in small amounts in most rocks and soils. Soil commonly contains an average of around 6 parts per million (ppm) of thorium. Thorium occurs...
Thorium heptaphosphide is a binary inorganic compound of thorium metal and phosphorus with the chemical formula ThP7. This is the most phosphorus-rich...
large resource of thorium. The beach sands of Kerala and Orissa have rich reserves of monazite, which contains about 8–10% thorium. Studies have been...
these metal oxides produce light from the heat of the flame whenever used. Thorium dioxide was commonly a major component; being radioactive, it has led to...
Thorium resources are the estimated mineral reserves of thorium on Earth. Thorium is a future potential source of low-carbon energy. Thorium has been demonstrated...
do, only thorium and uranium do so in more than trace quantities. The most abundant or easily synthesized actinides are uranium and thorium, followed...
Thorium trichloride is a binary inorganic compound of thorium metal and chlorine with the chemical formula ThCl3. The compound can be prepared by reducing...
thorium-230 with slow neutrons, converting it to the beta-decaying thorium-231; or, by irradiating thorium-232 with fast neutrons, generating thorium-231...
or actinide-relating minerals in the Earth's crust such as uranium and thorium. These minerals are helpful in many ways, such as carbon-dating, most detectors...
Thorium Wars is a vehicular combat video game developed by 3PM Games and published by Big John Games for Nintendo DS in 2009. Reception The game received...
reactor. Another fissile isotope, uranium-233, can be produced from natural thorium and is studied for future industrial use in nuclear technology. Uranium-238...
fueled with more-commonly available isotopes of uranium and thorium, such as uranium-238 and thorium-232, as opposed to the rare uranium-235 which is used in...
Thorium diiodide is an iodide of thorium, with the chemical formula of ThI2. It is an electride with the ionic formula Th4+(I-)2e-2. It is air-sensitive...
Thorium triiodide is a binary inorganic compound of thorium metal and iodine with the chemical formula ThI3. Th metal is heated with ThI4 in a vacuum...
Thorium triiodide is a binary inorganic compound of thorium metal and chloride with the chemical formula ThCl2. Th-metal is dissolved in alkali chloride...
Unbibium, also known as element 122 or eka-thorium, is a hypothetical chemical element; it has placeholder symbol Ubb and atomic number 122. Unbibium...
Thorium trifluoride is a binary inorganic compound of thorium metal and fluorine with the chemical formula ThF3. Reaction of thorium metal with thorium...