thorium standard state formula

[51] Thorium tetrafluoride has a monoclinic crystal structure like those of zirconium tetrafluoride and hafnium tetrafluoride, where the Th4+ ions are coordinated with F− ions in somewhat distorted square antiprisms. [150] 233Pa has a relatively long half-life of 27 days and a high cross section for neutron capture. Solvent extraction may also be used to separate out the thorium and uranium, by dissolving the resultant filter cake in nitric acid. 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. [10] Its stability is attributed to its closed nuclear subshell with 142 neutrons. In these deposits, thorium is enriched along with other heavy minerals. The metal is not attacked by the alkali hydroxides. List of Countries by Thorium Reserves Largest Thorium Reserves. . In the 1950s, India targeted achieving energy independence with their three-stage nuclear power programme. [29][111] Despite its radioactivity, the element has remained in use for applications where no suitable alternatives could be found. The standard enthalpy change of formation for an element in its standard state is zero, and this convention allows a wide range of other thermodynamic quantities to be calculated and tabulated. 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. [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. The number of electrons in each of thorium's shells is [2, 8, 18, 32, 18, 10, 2] and its electron configuration is [Rn] 6d 2 7s 2 . ", ground state electronic configuration of neutral thorium is. [160], Tests on the thorium uptake of workers involved in monazite processing showed thorium levels above recommended limits in their bodies, but no adverse effects on health were found at those moderately low concentrations. [118] Large-scale research was begun in 1996 by the International Atomic Energy Agency to study the use of thorium reactors; a year later, the United States Department of Energy started their research. 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. [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. 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. (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. Thorium is named for Thor, the Scandinavian god of war. This effect is shared by cerium dioxide, which converts ultraviolet light into visible light more efficiently, but thorium dioxide gives a higher flame temperature, emitting less infrared light. What is the standard state of magnesium? At present, information on resources of thorium ores is low since its low economic potential renders widespread exploration unnecessary. The only primordial elements rarer than thorium are thulium, lutetium, tantalum, and rhenium, the odd-numbered elements just before the third peak of r-process abundances around the heavy platinum group metals, as well as uranium. No chemical toxicity has yet been observed in the tracheobronchial tract and the lungs from exposure to thorium. In 1892, British chemist Henry Bassett postulated a second extra-long periodic table row to accommodate known and undiscovered elements, considering thorium and uranium to be analogous to the lanthanides. The work function from a thorium surface is lowered possibly because of the electric field on the interface between thorium and tungsten formed due to thorium's greater electropositivity. ", Thorium fuel cycle – Potential benefits and challenges, https://en.wikipedia.org/w/index.php?title=Thorium&oldid=988013117, Short description is different from Wikidata, Creative Commons Attribution-ShareAlike License. [6], Thorium is nearly half as dense as uranium and plutonium and is harder than both. This page was last edited on 10 November 2020, at 15:30. [135] According to the 2005 review by the United Kingdom's National Radiological Protection Board, "although [thoriated gas mantles] were widely available a few years ago, they are not any more. [29][83][86][87], In 1828, Morten Thrane Esmark found a black mineral on Løvøya island, Telemark county, Norway. [77][81] Monazite is a chemically unreactive mineral that is found as yellow or brown sand; its low reactivity makes it difficult to extract thorium from it. In the first hour of use large fractions of the thorium daughters 224Ra, 228Ra, 212Pb, and 212Bi are released. 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[83] Berzelius privately named the putative element "thorium" in 1817[84] and its supposed oxide "thorina" after Thor, the Norse god of thunder. [100][101][102] Starting from 1899, the New Zealand physicist Ernest Rutherford and the American electrical engineer Robert Bowie Owens studied the radiation from thorium; initial observations showed that it varied significantly. When pure, thorium is a silvery white metal which is air-stable and retains its lustre for several months. Since dissolution is very exothermic, the monazite sand cannot be added to the acid too quickly. Most widespread minerals containing Thorium; This list of minerals containing Thorium is built from the mindat.org locality database. [51] For example, when treated with potassium fluoride and hydrofluoric acid, Th4+ forms the complex anion ThF2−6, which precipitates as an insoluble salt, K2ThF6. Thorium is still being used as an alloying element in TIG welding electrodes but is slowly being replaced in the field with different compositions. Thorium is a weakly radioactive metallic chemical element with the symbol Th and atomic number 90. [4] Experimental measurements of its density give values between 11.5 and 11.66 g/cm3: these are slightly lower than the theoretically expected value of 11.7 g/cm3 calculated from thorium's lattice parameters, perhaps due to microscopic voids forming in the metal when it is cast. In natural thorium-containing waters, organic thorium complexes usually occur in concentrations orders of magnitude higher than the inorganic complexes, even when the concentrations of inorganic ligands are much greater than those of organic ligands. Thorium is silvery and tarnishes black when it is exposed to air, forming thorium dioxide; it is moderately hard, 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. [10], In deep seawaters the isotope 230Th makes up to 0.04% of natural thorium. [c], The properties of thorium vary widely depending on the degree of impurities in the sample. [7], Tetravalent thorium compounds are usually colourless or yellow, like those of silver or lead, as the Th4+ ion has no 5f or 6d electrons. Thus it is a neutron poison: instead of rapidly decaying to the useful 233U, a significant amount of 233Pa converts to 234U and consumes neutrons, degrading the reactor efficiency. [152], The irradiation of 232Th with neutrons, followed by its processing, need to be mastered before these advantages can be realised, and this requires more advanced technology than the uranium and plutonium fuel cycle;[29] research continues in this area. [46] Public interest in radioactivity had declined by the end of the 1930s. The mineral contained a large number of known elements including iron, manganese, lead, tin and uraniumplus another substance Berzelius could not identify. [a] It 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. Following filtration, the filter cake includes thorium and the rare earths as their hydroxides, uranium as sodium diuranate, and phosphate as trisodium phosphate. Nine people were injured; one died of complications caused by third-degree burns. The Metals. He called the blac… Thorium is less radioactive than uranium. Alpha decay is a type of radioactive decayin which a particle with two neutrons and two protons is ejected from the nucleus of a radioactive atom. They decompose slowly at room temperature. [59] They are important in thorium purification and the disposal of nuclear waste, but most of them have not yet been fully characterized, especially regarding their structural properties. Primary deposits occur in acidic granitic magmas and pegmatites. Although one methyl group is only attached to the thorium atom (Th–C distance 257.1 pm) and the other six connect the lithium and thorium atoms (Th–C distances 265.5–276.5 pm), they behave equivalently in solution. [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. Four-fifths of the thorium present at Earth's formation has survived to the present. Uranium ores with low thorium concentrations can be purified to produce gram-sized thorium samples of which over a quarter is the 230Th isotope, since 230Th is one of the daughters of 238U. Like many of the early and middle actinides (up to americium, and also expected for curium), thorium forms a cyclooctatetraenide complex: the yellow Th(C8H8)2, thorocene. The introduction of transistors in the 1950s significantly diminished this use, but not entirely. Secondary deposits occur at the mouths of rivers in granitic mountain regions. [39] Initial concentration varies with the type of deposit. Therefore 232 Th belongs to primordial nuclides.. 232 Th decays via alpha decay into 228 Ra . [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. Top Answer. This method relied on the specifics of the technique and the concentrate grain size; many alternatives have been proposed, but only one has proven effective economically: alkaline digestion with hot sodium hydroxide solution. 232Th absorbs neutrons more readily than 238U, and 233U has a higher probability of fission upon neutron capture (92.0%) than 235U (85.5%) or 239Pu (73.5%). This has been blamed for a high incidence of birth defects and cancer at Salto di Quirra on the Italian island of Sardinia.[173]. [170] Thorium is especially common in the Tamil Nadu coastal areas of India, where residents may be exposed to a naturally occurring radiation dose ten times higher than the worldwide average. Other uses for thorium include heat-resistant ceramics, aircraft engines, and in light bulbs. De eerste praktische toepassing van thorium was in gaskousjes in draagbare gaslampen, door Welsbach, aan het einde van de 19e eeuw.Deze gaskousjes bestonden uit thoriumoxide plus 1% cesiumoxide en nog andere stoffen. 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. [134] Thorium in mantles, though still common, has been progressively replaced with yttrium since the late 1990s. [21][i], Thorium only occurs as a minor constituent of most minerals, and was for this reason previously thought to be rare. [69] This is because thorium is likely to form oxide minerals that do not sink into the core; it is classified as a lithophile. 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. Swedish chemist, Thorium also appears in the 1864 table by British chemist. [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. [132], For the primary deposits, the source pegmatites, which are usually obtained by mining, are divided into small parts and then undergo flotation. [113] As recently as 2007, some companies continued to manufacture and sell thorium mantles without giving adequate information about their radioactivity, with some even falsely claiming them to be non-radioactive. [l], In the periodic table published by Dmitri Mendeleev in 1869, thorium and the rare-earth elements were placed outside the main body of the table, at the end of each vertical period after the alkaline earth metals. [121][122][123] India has projected meeting as much as 30% of its electrical demands through thorium-based nuclear power by 2050. Thorium atoms have 90 electrons and the shell structure is 2.8.18.32.18.10.2. The rare earths again precipitate out at higher pH. [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. [60] It is unstable in air and decomposes in water or at 190 °C. 235U occurs naturally and is also fissile. Powdered thorium metal is often pyrophoric and should be carefully handled. This reflected the belief at that time that thorium and the rare-earth metals were divalent. Berzelius determined that it contained a new element. [146] A single neutron capture by 238U produces transuranic waste along with the fissile 239Pu, but 232Th only produces this waste after five captures, forming 237Np. It is found in thorite and thorianite in New England (USA) and other sites. Three of the sets, the thorium series, uranium series, and actinium series, called natural or classical series, are headed by naturally occurring species of unstable nuclei that have half-lives comparable to the age of the elements. An alloy of 90% platinum and 10% thorium is an effective catalyst for oxidising ammonia to nitrogen oxides, but this has been replaced by an alloy of 95% platinum and 5% rhodium because of its better mechanical properties and greater durability. [115] One of the largest supplies of thorium in the world is in the country of India, where there is not much uranium. [49], Several binary thorium chalcogenides and oxychalcogenides are also known with sulfur, selenium, and tellurium. [37][g] Thorium and uranium are the most investigated of the radioactive elements because their radioactivity is low enough not to require special handling in the laboratory. On Earth, thorium, bismuth, and uranium are the only three radioactive elements that still occur naturally in large quantities as primordial elements. [46] Thorium has no known biological role. All of the remaining thorium isotopes have half-lives that are less than thirty days and the majority of these have half-lives that are less than ten minutes. The scheme has a range of several hundred thousand years. The Th 4+ ion forms many complex ions. Favorite Answer. Gamma rays are distinguished by their origin in the nucleus, not their wavelength; hence there is no lower limit to gamma energy derived from radioactive decay. 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. These reaction conditions are rather mild and require monazite sand with a particle size under 45 μm. Tetrabenzylthorium, Th(CH2C6H5), and tetraallylthorium, Th(C3H5)4, are known, but their structures have not been determined. 40% Thorium Ore is an ore which generates naturally upon world creation. [16][17] 227Th (alpha emitter with an 18.68 days half-life) can also be used in cancer treatments such as targeted alpha therapies. [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). [132], There are two categories of thorium minerals for thorium extraction: primary and secondary. 3 4 5. Like all metals except for Mercury thorium's standard state is solid. [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. Its radiation is primarily due to alpha particles, which can be easily stopped by a thin cover layer of another material. Thorium(IV) hydroxide can be produced by reacting sodium hydroxide and soluble thorium salts. [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. [59] Thorium complexes with organic ligands, such as oxalate, citrate, and EDTA, are much more stable. 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. The actual crystal structure can only be explained when the 5f states are invoked, proving that thorium, and not protactinium, acts as the first actinide metallurgically. [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. Start studying Elements in Standard State. The closeness in energy levels of the 5f, 6d, and 7s energy levels of thorium results in thorium almost always losing all four valence electrons and occurring in its highest possible oxidation state of +4. In the second half of the century, thorium was replaced in many uses due to concerns about its radioactivity. This is based on the number of localities entered for mineral species and is therefore slanted towards minerals interesting to collectors with less coverage of common rock-forming-minerals so it does not give an undistorted distribution of Thorium mineral species. Alkaline earth metal carbonates may be removed after reaction with hydrogen chloride; then follow thickening, filtration, and calcination. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Thorium 232, which alone makes up nearly all natural thorium, is the most common isotope of thorium in the nature.This isotope has the longest half-life (1.4 x 10 10 years) of all isotopes with more than 83 protons. Its minimum explosive concentration was listed as 0.075 oz/cu ft (0.075 kg/m3); the minimum igniting energy for (non-submicron) dust was listed as 5 mJ. [4][42][43], Most binary compounds of thorium with nonmetals may be prepared by heating the elements together. [157] Exposure to an aerosol of thorium, such as contaminated dust, can lead to increased risk of cancers of the lung, pancreas, and blood, as lungs and other internal organs can be penetrated by alpha radiation. [5] Thorium is about as hard as soft steel, so when heated it can be rolled into sheets and pulled into wire. [104] The biological effect of radiation was discovered in 1903. It can take as much as thirty years after the ingestion of thorium for symptoms to manifest themselves. [157] Thorium's low solubility in water also means that excretion of thorium by the kidneys and faeces is rather slow. Thorium is much more similar to the transition metals zirconium and hafnium than to cerium in its ionization energies and redox potentials, and hence also in its chemistry: this transition-metal-like behaviour is the norm in the first half of the actinide series. [15] The alpha decay of 232Th initiates the 4n decay chain which includes isotopes with a mass number divisible by 4 (hence the name; it is also called the thorium series after its progenitor). [6][7] (The f-electron count for thorium metal is a non-integer due to a 5f–6d overlap. This compound has a melting point of 3300 °C (6000 °F), the highest of all known oxides; only a few substances have higher melting points. This is due to relativistic effects, which become stronger near the bottom of the periodic table, specifically the relativistic spin–orbit interaction. Monazite obtained by this method can be as pure as 98%. [4] At room temperature, thorium metal has a face-centred cubic crystal structure; it has two other forms, one at high temperature (over 1360 °C; body-centred cubic) and one at high pressure (around 100 GPa; body-centred tetragonal). The standard state of a substance does not have to exist in nature: for example, it is possible to calculate values for steam at 25 °C and 1 bar, even though steam does not exist (as a gas) under … When contaminated with the oxide, thorium slowly tarnishes in air, becoming grey and finally black. Bond strengths; lattice energies of thorium halides, hydrides, oxides (where known); and reduction potentials where known. The decay chain is known as thorium series that will result in a stable 208 Pb. [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. [77] Because of the great insolubility of thorium dioxide, thorium does not usually spread quickly through the environment when released. In fact, its half-life is considerably longer than the age of earth. [103], After accounting for the contribution of radon, Rutherford, now working with the British physicist Frederick Soddy, showed how thorium decayed at a fixed rate over time into a series of other elements in work dating from 1900 to 1903. [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. [51] The other tetrahalides instead have dodecahedral geometry. It was determined that these variations came from a short-lived gaseous daughter of thorium, which they found to be a new element. [13][14] Thorium has a characteristic terrestrial isotopic composition, with atomic weight 232.0377(4). [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. [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). [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. [152], Natural thorium decays very slowly compared to many other radioactive materials, and the emitted alpha radiation cannot penetrate human skin. [172], Another possible source of exposure is thorium dust produced at weapons testing ranges, as thorium is used in the guidance systems of some missiles. He concluded that the mineral contained a new element. [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. "[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. [106] 10,000 individuals in the United States had been injected with thorium during X-ray diagnosis; they were later found to suffer health issues such as leukaemia and abnormal chromosomes. 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. In addition to being crafted, they can also be obtained from Scarlet Chests, as well as from Strange Crates and Scarlet Crates. [39] Finely divided thorium metal can exhibit pyrophoricity, spontaneously igniting in air. Today, liquid solvent extraction procedures involving selective complexation of Th4+ are used. It was hypothesized that the 233U would then be usable in a gun-type weapon, though concerns about contamination from 232U were voiced. Thorium forms the monocapped trigonal prismatic anion [Th(CH3)7]3−, heptamethylthorate, which forms the salt [Li(tmeda)]3[ThMe7] (tmeda= Me2NCH2CH2NMe2). Berzelius had already discovered two elements, cerium and selenium, but he had made a public mistake once, announcing a new element, gahnium, that turned out to be zinc oxide. Thorium is slowly attacked by water, but does not dissolve readily in most common acids, except hydrochloric. [157] Internal exposure to thorium leads to increased risk of liver diseases. 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. They are concentrated, but of small size. [29][111], Most thorium applications use its dioxide (sometimes called "thoria" in the industry), rather than the metal. 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. [28][29], Two radiometric dating methods involve thorium isotopes: uranium–thorium dating, based on the decay of 234U to 230Th, and ionium–thorium dating, which measures the ratio of 232Th to 230Th. Thorium is also used to strengthen magnesium, coating tungsten wire in electrical equipment, controlling the grain size of tungsten in electric lamps, high-temperature crucibles, in glasses and used in camera and scientific instrument lenses.

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