Progress on the implosion weapon was sufficient, and this converter was not developed further, but the design had enormous influence on the development of nuclear energy. Previously, repeated dissolution and recrystallisation was used to achieve high purity. [40] The radiation from these lenses can darken them and turn them yellow over a period of years and it degrades film, but the health risks are minimal. [50], All four thorium tetrahalides are known, as are some low-valent bromides and iodides:[51] the tetrahalides are all 8-coordinated hygroscopic compounds that dissolve easily in polar solvents such as water. [46] Thorium has no known biological role. There is probably more untapped energy available for use from thorium in the minerals of the earth's crust than from combined uranium and fossil fuel sources. [138][139], Thorium dioxide is found in heat-resistant ceramics, such as high-temperature laboratory crucibles,[29] either as the primary ingredient or as an addition to zirconium dioxide. [29][111], Most thorium applications use its dioxide (sometimes called "thoria" in the industry), rather than the metal. Monazite obtained by this method can be as pure as 98%. This is more expensive than the original method but yields a higher purity of thorium; in particular, it removes phosphates from the concentrate. It was the second element that was found to be radioactive, after the 1896 discovery of radioactivity in uranium by French physicist Henri Becquerel. [59] For example, thorium nitrate is produced by reacting thorium hydroxide with nitric acid: it is soluble in water and alcohols and is an important intermediate in the purification of thorium and its compounds. Copyright 1993-2020 Mark Winter [ The University of Sheffield and WebElements Ltd, UK]. Answer. The precipitates are neutralised by the original sodium hydroxide solution, although most of the phosphate must first be removed to avoid precipitating rare-earth phosphates. [106], Up to the late 19th century, chemists unanimously agreed that thorium and uranium were analogous to hafnium and tungsten; the existence of the lanthanides in the sixth row was considered to be a one-off fluke. 0. [70], Thorium is the 41st most abundant element in the Earth's crust. It can take as much as thirty years after the ingestion of thorium for symptoms to manifest themselves. [29] This parallels the uranium fuel cycle in fast breeder reactors where 238U undergoes neutron capture to become 239U, beta decaying to first 239Np and then fissile 239Pu. [133] Thorium dioxide is used in gas tungsten arc welding (GTAW) to increase the high-temperature strength of tungsten electrodes and improve arc stability. The metal is not attacked by the alkali hydroxides. [140] Yellowed lenses may be restored to their original colourless state by lengthy exposure to intense ultraviolet radiation. [132], Industrial production in the 20th century relied on treatment with hot, concentrated sulfuric acid in cast iron vessels, followed by selective precipitation by dilution with water, as on the subsequent steps. These reaction conditions are rather mild and require monazite sand with a particle size under 45 μm. [96] The existence of a second inner transition series, in the form of the actinides, was not accepted until similarities with the electron structures of the lanthanides had been established;[107] Bohr suggested that the filling of the 5f orbitals may be delayed to after uranium. "[136], During the production of incandescent filaments, recrystallisation of tungsten is significantly lowered by adding small amounts of thorium dioxide to the tungsten sintering powder before drawing the filaments. In bulk, the reaction of pure thorium with air is slow, although corrosion may occur after several months; most thorium samples are contaminated with varying degrees of the dioxide, which greatly accelerates corrosion. Natural thorium is usually almost pure 232Th, which is the longest-lived and most stable isotope of thorium, having a half-life comparable to the age of the universe. [4][42][43], Most binary compounds of thorium with nonmetals may be prepared by heating the elements together. [114] Three-quarters of the thorium that has penetrated the body accumulates in the skeleton. Infobox references By mixing 0.5 M thorium nitrate solution with 0.5 M oxalic acid solution at room temperature thorium oxalate dihydrate ( Th ( C 2 O 4 ) 2 ⋅ 2 H 2 O {\displaystyle {\ce {Th(C2O4)2.2H2O}}} ) is obtained. )[7] Among the actinides up to californium, which can be studied in at least milligram quantities, thorium has the highest melting and boiling points and second-lowest density; only actinium is lighter. 0 0 1. [46], In 1815, the Swedish chemist Jöns Jacob Berzelius analysed an unusual sample of gadolinite from a copper mine in Falun, central Sweden. 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. Eugene Wigner proposed to use the 240Pu-contaminated plutonium to drive the conversion of thorium into 233U in a special converter reactor. To avoid this, 233Pa is extracted from the active zone of thorium molten salt reactors during their operation, so that it does not have a chance to capture a neutron and will only decay to 233U. [52] Lower iodides ThI3 (black) and ThI2 (gold-coloured) can also be prepared by reducing the tetraiodide with thorium metal: they do not contain Th(III) and Th(II), but instead contain Th4+ and could be more clearly formulated as electride compounds. . [115] One of the largest supplies of thorium in the world is in the country of India, where there is not much uranium. [46] The other natural thorium isotopes are much shorter-lived; of them, only 230Th is usually detectable, occurring in secular equilibrium with its parent 238U, and making up at most 0.04% of natural thorium. Answer to: Write a complete chemical formula including physical state symbol, for each element listed below in its standard state. The mineral contained a large number of known elements including iron, manganese, lead, tin and uraniumplus another substance Berzelius could not identify. 7s2 and the term symbol of thorium is 3F2. Although relatively little of those products are created as the result of the slow decay of thorium, a proper assessment of the radiological toxicity of 232Th must include the contribution of its daughters, some of which are dangerous gamma emitters,[159] and which are built up quickly following the initial decay of 232Th due to the absence of long-lived nuclides along the decay chain. Only a few elements, such as tungsten, and a few compounds, such as tantalum carbide, have higher melting points. [34] Despite thorium's position in the f-block of the periodic table, it has an anomalous [Rn]6d27s2 electron configuration in the ground state, as the 5f and 6d subshells in the early actinides are very close in energy, even more so than the 4f and 5d subshells of the lanthanides: thorium's 6d subshells are lower in energy than its 5f subshells, because its 5f subshells are not well-shielded by the filled 6s and 6p subshells and are destabilized. He noted impregnated traces of a white mineral, which he cautiously assumed to be an earth (oxide in modern chemical nomenclature) of an unknown element. In the second half of the century, thorium was replaced in many uses due to concerns about its radioactivity. Image adapted with permission from Prof James Marshall's (U. The result is a concentrate with rare-earth content of up to 90%. [156] The isotopes produced in the thorium fuel cycle are mostly not transuranic, but some of them are still very dangerous, such as 231Pa, which has a half-life of 32,760 years and is a major contributor to the long-term radiotoxicity of spent nuclear fuel. [129] Present knowledge of the distribution of thorium resources is poor, as low demand has led to exploration efforts being relatively minor. [125] They concluded that a 233U-fired bomb would be a very potent weapon, but it bore few sustainable "technical advantages" over the contemporary uranium–plutonium bombs,[126] especially since 233U is difficult to produce in isotopically pure form. [30][31] Ionium–thorium dating is a related process, which exploits the insolubility of thorium (both 232Th and 230Th) and thus its presence in ocean sediments to date these sediments by measuring the ratio of 232Th to 230Th. [134] Thorium in mantles, though still common, has been progressively replaced with yttrium since the late 1990s. [56] The Th4+ ion is the largest of the tetrapositive actinide ions, and depending on the coordination number can have a radius between 0.95 and 1.14 Å. [4] These values lie between those of its neighbours actinium (10.1 g/cm3) and protactinium (15.4 g/cm3), part of a trend across the early actinides. The state elements are in at 1 atm and 25 C Learn with flashcards, games, and more — for free. Powdered thorium metal is often pyrophoric and should be carefully handled.When heated in air, thorium turnings ignite and burn brilliantly with a white light. [30] Uranium–thorium dating is a relatively short-range process because of the short half-lives of 234U and 230Th relative to the age of the Earth: it is also accompanied by a sister process involving the alpha decay of 235U into 231Th, which very quickly becomes the longer-lived 231Pa, and this process is often used to check the results of uranium–thorium dating. [58] As a hard Lewis acid, Th4+ favours hard ligands with oxygen atoms as donors: complexes with sulfur atoms as donors are less stable and are more prone to hydrolysis. This is due to relativistic effects, which become stronger near the bottom of the periodic table, specifically the relativistic spin–orbit interaction. [93] Metallic thorium was isolated for the first time in 1914 by Dutch entrepreneurs Dirk Lely Jr. and Lodewijk Hamburger. Solvent extraction may also be used to separate out the thorium and uranium, by dissolving the resultant filter cake in nitric acid. )[75] Its decay accounts for a gradual decrease of thorium content of the Earth: the planet currently has around 85% of the amount present at the formation of the Earth. This element is now named radon, the only one of the rare radioelements to be discovered in nature as a daughter of thorium rather than uranium. [146] All 233U production methods result in impurities of 232U, either from parasitic knock-out (n,2n) reactions on 232Th, 233Pa, or 233U that result in the loss of a neutron, or from double neutron capture of 230Th, an impurity in natural 232Th:[150], 232U by itself is not particularly harmful, but quickly decays to produce the strong gamma emitter 208Tl. Thorium standard state formula keyword after analyzing the system lists the list of keywords related and the list of websites with related content, in addition you can see which keywords most interested customers on the this website [158], Thorium is odourless and tasteless. [4] Such samples slowly tarnish, becoming grey and finally black at the surface. 3 4 5. For example, following alkaline digestion and the removal of phosphate, the resulting nitrato complexes of thorium, uranium, and the rare earths can be separated by extraction with tributyl phosphate in kerosene. [49], Energy, some of it in the form of visible light, is emitted when thorium is exposed to a source of energy itself, such as a cathode ray, heat, or ultraviolet light. He called the blac… Mag-Thor alloys (also called thoriated magnesium) found use in some aerospace applications, though such uses have been phased out due to concerns over radioactivity. The mixture is then cooled to 70 °C and diluted with ten times its volume of cold water, so that any remaining monazite sinks to the bottom while the rare earths and thorium remain in solution. Learn vocabulary, terms, and more with flashcards, games, and other study tools. [125], Thorium metal was used in the radiation case of at least one nuclear weapon design deployed by the United States (the W71). [60] It is unstable in air and decomposes in water or at 190 °C. Its ignition temperature was given as 270 °C (520 °F) for dust clouds and 280 °C (535 °F) for layers. [124], During the Cold War the United States explored the possibility of using 232Th as a source of 233U to be used in a nuclear bomb; they fired a test bomb in 1955. 235U occurs naturally and is also fissile. Since dissolution is very exothermic, the monazite sand cannot be added to the acid too quickly. [99], Thorium was first observed to be radioactive in 1898, by the German chemist Gerhard Carl Schmidt and later that year, independently, by the Polish-French physicist Marie Curie. Thorium Bars are crafted with 4 Thorium Ore at a Thorium Anvil, and are one of the first tier of crafting materials. It is transparent to electromagnetic waves having wavelengths in the range of 0.350–12 µm, a range that includes near ultraviolet, visible and mid infrared light. Reactions of thorium as the element with air, water, halogens, acids, and bases where known. [6] Thorium chemistry is therefore largely that of an electropositive metal forming a single diamagnetic ion with a stable noble-gas configuration, indicating a similarity between thorium and the main group elements of the s-block. [80], Monazite (chiefly phosphates of various rare-earth elements) is the most important commercial source of thorium because it occurs in large deposits worldwide, principally in India, South Africa, Brazil, Australia, and Malaysia. [58] These thorium salts are known for their high solubility in water and polar organic solvents. [98][n], In the 1990s, most applications that do not depend on thorium's radioactivity declined quickly due to safety and environmental concerns as suitable safer replacements were found. [157] Thorium's low solubility in water also means that excretion of thorium by the kidneys and faeces is rather slow. Solid. [145], Thorium is more abundant than uranium, and can satisfy world energy demands for longer.[146]. Thorium fuels result in a safer and better-performing reactor core[29] because thorium dioxide has a higher melting point, higher thermal conductivity, and a lower coefficient of thermal expansion. WebElements: THE periodic table on the WWW [www.webelements.com] ", ground state electronic configuration of neutral thorium is. This is different from its lanthanide congener cerium, in which +4 is also the highest possible state, but +3 plays an important role and is more stable. [35], 232Th is a primordial nuclide, having existed in its current form for over ten billion years; it was forged in the cores of dying stars through the r-process and scattered across the galaxy by supernovae and neutron star mergers. [10] Any sample of thorium or its compounds contains traces of these daughters, which are isotopes of thallium, lead, bismuth, polonium, radon, radium, and actinium. 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. Production. [162], Some nuclear safety agencies make recommendations about the use of thorium mantles and have raised safety concerns regarding their manufacture and disposal; the radiation dose from one mantle is not a serious problem, but that from many mantles gathered together in factories or landfills is. Pure thorium is very ductile and, as normal for metals, can be cold-rolled, swaged, and drawn. Reactions. [4], All but two elements up to bismuth (element 83) have an isotope that is practically stable for all purposes ("classically stable"), with the exceptions being technetium and promethium (elements 43 and 61). [158], The decay products of 232Th include more dangerous radionuclides such as radium and radon. [166], In 1956, the Sylvania Electric Products explosion occurred during reprocessing and burning of thorium sludge in New York City, United States. 2011-09-25 11:21:34. [133], When added to glass, thorium dioxide helps increase its refractive index and decrease dispersion. New thorium(IV) hydroxide is soluble in acid but its solubility will decrease when older. A 1981 study by the Oak Ridge National Laboratory in the United States estimated that using a thorium gas mantle every weekend would be safe for a person,[111] but this was not the case for the dose received by people manufacturing the mantles or for the soils around some factory sites. [63][65][h] In the distant past the abundances of thorium and uranium were enriched by the decay of plutonium and curium isotopes, and thorium was enriched relative to uranium by the decay of 236U to 232Th and the natural depletion of 235U, but these sources have long since decayed and no longer contribute. [16][17] 227Th (alpha emitter with an 18.68 days half-life) can also be used in cancer treatments such as targeted alpha therapies. Anonymous. The concentration of the sulfuric acid is selected based on reaction rate and viscosity, which both increase with concentration, albeit with viscosity retarding the reaction. Thorium forms the monocapped trigonal prismatic anion [Th(CH3)7]3−, heptamethylthorate, which forms the salt [Li(tmeda)]3[ThMe7] (tmeda= Me2NCH2CH2NMe2). Magnetic separation follows, with a series of magnets of increasing strength. [98][m], While thorium was discovered in 1828 its first application dates only from 1885, when Austrian chemist Carl Auer von Welsbach invented the gas mantle, a portable source of light which produces light from the incandescence of thorium oxide when heated by burning gaseous fuels. Thorium dioxide has since been replaced in this application by rare-earth oxides, such as lanthanum, as they provide similar effects and are not radioactive.[133]. The Th 4+ ion forms many complex ions. [132], For the primary deposits, the source pegmatites, which are usually obtained by mining, are divided into small parts and then undergo flotation. Thorium may then be separated by precipitating it as the phosphate at pH 1.3, since the rare earths do not precipitate until pH 2. Four-fifths of the thorium present at Earth's formation has survived to the present. (At the time of the Earth's formation, 40K and 235U contributed much more by virtue of their short half-lives, but they have decayed more quickly, leaving the contribution from 232Th and 238U predominant. [130] In 2014, world production of the monazite concentrate, from which thorium would be extracted, was 2,700 tonnes. [133] A small addition of thorium to tungsten thermocathodes considerably reduces the work function of electrons; as a result, electrons are emitted at considerably lower temperatures. [53] Thorium reacts with hydrogen to form the thorium hydrides ThH2 and Th4H15, the latter of which is superconducting below 7.5–8 K; at standard temperature and pressure, it conducts electricity like a metal. In February 2014, Bhabha Atomic Research Centre (BARC), in Mumbai, India, presented their latest design for a "next-generation nuclear reactor" that burns thorium as its fuel ore, calling it the Advanced Heavy Water Reactor (AWHR). Thorium is a weakly radioactive metallic chemical element with the symbol Th and atomic number 90. [55], In an acidic aqueous solution, thorium occurs as the tetrapositive aqua ion [Th(H2O)9]4+, which has tricapped trigonal prismatic molecular geometry:[56][57] at pH < 3, the solutions of thorium salts are dominated by this cation. [65] Because of the abrupt loss of stability past 209Bi, the r-process is the only process of stellar nucleosynthesis that can create thorium and uranium; all other processes are too slow and the intermediate nuclei alpha decay before they capture enough neutrons to reach these elements. [119] He founded a consortium to develop thorium reactors, which included other laboratories: Raytheon Nuclear Inc. and Brookhaven National Laboratory in the United States, and the Kurchatov Institute in Russia. [77] Allanite (chiefly silicates-hydroxides of various metals) can have 0.1–2% thorium and zircon (chiefly zirconium silicate, ZrSiO4) up to 0.4% thorium. This is so low that when it undergoes isomeric transition, the emitted gamma radiation is in the ultraviolet range. [56], Most of the work on organothorium compounds has focused on the cyclopentadienyl complexes and cyclooctatetraenyls. [163] The chemical toxicity of thorium is low because thorium and its most common compounds (mostly the dioxide) are poorly soluble in water,[164] precipitating out before entering the body as the hydroxide. [148] Liquid fluoride thorium reactors (LFTR) have very little waste compared with reactors powered by uranium. [46], Powdered thorium metal is pyrophoric: it ignites spontaneously in air. 232Th is one of the three nuclides beyond bismuth (the other two being 235U and 238U) that have half-lives measured in billions of years; its half-life is 14.05 billion years, about three times the age of the earth, and slightly longer than the age of the universe. When 233U undergoes nuclear fission, the neutrons emitted can strike further 232Th nuclei, continuing the cycle. [4], Thorium metal has a bulk modulus (a measure of resistance to compression of a material) of 54 GPa, about the same as tin's (58.2 GPa). Thorium atoms have 90 electrons and the shell structure is 2.8.18.32.18.10.2. [41], Thorium borides, carbides, silicides, and nitrides are refractory materials, like those of uranium and plutonium, and have thus received attention as possible nuclear fuels. To ensure that no precipitates form to block the reactive monazite surface, the mass of acid used must be twice that of the sand, instead of the 60% that would be expected from stoichiometry. The introduction of transistors in the 1950s significantly diminished this use, but not entirely. [149], The used fuel is difficult and dangerous to reprocess because many of the daughters of 232Th and 233U are strong gamma emitters. This observation led to the identification of the half-life as one of the outcomes of the alpha particle experiments that led to the disintegration theory of radioactivity. Powdered thorium metal is often pyrophoric and should be carefully handled. [160] As the dangerous daughters of thorium have much lower melting points than thorium dioxide, they are volatilised every time the mantle is heated for use. In addition to being crafted, they can also be obtained from Scarlet Chests, as well as from Strange Crates and Scarlet Crates. Asked by Wiki User. The model indicated that the seventh row of the periodic table should also have f-shells filling before the d-shells that were filled in the transition elements, like the sixth row with the lanthanides preceding the 5d transition metals. Then, fuming sulfuric acid is added and the mixture is kept at the same temperature for another five hours to reduce the volume of solution remaining after dilution. It was hypothesized that the 233U would then be usable in a gun-type weapon, though concerns about contamination from 232U were voiced. It can be mined with an Iron Pickaxe or better. [60] Half sandwich compounds are also known, such as (η8-C8H8)ThCl2(THF)2, which has a piano-stool structure and is made by reacting thorocene with thorium tetrachloride in tetrahydrofuran. The filling of the 5f subshell from the beginning of the actinide series was confirmed in 1964 when the next element, The thirteen fissile actinide isotopes with half-lives over a year are, International Union of Pure and Applied Chemistry, tricapped trigonal prismatic molecular geometry, An even number of either protons or neutrons, "Atomic weights of the elements 2013 (IUPAC Technical Report)", "Anomalous fcc crystal structure of thorium metal", "The NUBASE evaluation of nuclear and decay properties", "Atomic weights of the elements. Following filtration, the filter cake includes thorium and the rare earths as their hydroxides, uranium as sodium diuranate, and phosphate as trisodium phosphate. The ground state electronic configuration of neutral thorium is [Rn].6d2.7s2 and the term symbol of thorium is 3F2. Due to its being isotypic with uranium dioxide, these two common actinide dioxides can form solid-state solutions and the name of the mineral changes according to the ThO2 content. All of these isotopes occur in nature as trace radioisotopes due to their presence in the decay chains of 232Th, 235U, 238U, and 237Np: the last of these is long extinct in nature due to its short half-life (2.14 million years), but is continually produced in minute traces from neutron capture in uranium ores. This page was last edited on 10 November 2020, at 15:30. [f] These rely on the fact that 232Th is a primordial radioisotope, but 230Th only occurs as an intermediate decay product in the decay chain of 238U. This chain of consecutive alpha and beta decays begins with the decay of 232Th to 228Ra and terminates at 208Pb. [171] It is also common in northern Brazilian coastal areas, from south Bahia to Guarapari, a city with radioactive monazite sand beaches, with radiation levels up to 50 times higher than world average background radiation. Thorium may be three times more abundant on Earth than uranium, it is difficult to estimate, and can also be used in nuclear reactors. [35][36], Despite the anomalous electron configuration for gaseous thorium atoms, metallic thorium shows significant 5f involvement. Primary deposits occur in acidic granitic magmas and pegmatites. [137] Since the 1920s, thoriated tungsten wires have been used in electronic tubes and in the cathodes and anticathodes of X-ray tubes and rectifiers. [44] In air, thorium burns to form ThO2, which has the fluorite structure. Therefore 232 Th belongs to primordial nuclides.. 232 Th decays via alpha decay into 228 Ra . )[151] These impurities of 232U make 233U easy to detect and dangerous to work on, and the impracticality of their separation limits the possibilities of nuclear proliferation using 233U as the fissile material. 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