176-579: The rare-earth elements ( REE ), also called the rare-earth metals or rare earths , and sometimes the lanthanides or lanthanoids (although scandium and yttrium , which do not belong to this series, are usually included as rare earths), are a set of 17 nearly indistinguishable lustrous silvery-white soft heavy metals . Compounds containing rare earths have diverse applications in electrical and electronic components, lasers, glass, magnetic materials, and industrial processes. Scandium and yttrium are considered rare-earth elements because they tend to occur in
352-425: A body-centered cubic structure and is the more stable form. The structure of the β phase is called A15 cubic ; it is metastable , but can coexist with the α phase at ambient conditions owing to non-equilibrium synthesis or stabilization by impurities. Contrary to the α phase which crystallizes in isometric grains, the β form exhibits a columnar habit . The α phase has one third of the electrical resistivity and
528-549: A fissile material . The principal sources of rare-earth elements are the minerals bastnäsite ( RCO 3 F , where R is a mixture of rare-earth elements), monazite ( XPO 4 , where X is a mixture of rare-earth elements and sometimes thorium), and loparite ( (Ce,Na,Ca)(Ti,Nb)O 3 ), and the lateritic ion-adsorption clays . Despite their high relative abundance, rare-earth minerals are more difficult to mine and extract than equivalent sources of transition metals (due in part to their similar chemical properties), making
704-436: A negative ion . However, owing to widespread current use, lanthanide is still allowed. Primordial From decay Synthetic Border shows natural occurrence of the element The term "lanthanide" was introduced by Victor Goldschmidt in 1925. Despite their abundance, the technical term "lanthanides" is interpreted to reflect a sense of elusiveness on the part of these elements, as it comes from
880-437: A sextuple bond between tungsten atoms — the highest known bond order among stable atoms. In 1781, Carl Wilhelm Scheele discovered that a new acid , tungstic acid , could be made from scheelite (at the time called tungsten). Scheele and Torbern Bergman suggested that it might be possible to obtain a new metal by reducing this acid. In 1783, José and Fausto Elhuyar found an acid made from wolframite that
1056-592: A CO 2 -rich primary magma, by fractional crystallization of an alkaline primary magma, or by separation of a CO 2 -rich immiscible liquid from. These liquids are most commonly forming in association with very deep Precambrian cratons , like the ones found in Africa and the Canadian Shield. Ferrocarbonatites are the most common type of carbonatite to be enriched in REE, and are often emplaced as late-stage, brecciated pipes at
1232-545: A NiAs type structure and can be formulated La (I )(e ) 2 . TmI is a true Tm(I) compound, however it is not isolated in a pure state. All of the lanthanides form sesquioxides, Ln 2 O 3 . The lighter/larger lanthanides adopt a hexagonal 7-coordinate structure while the heavier/smaller ones adopt a cubic 6-coordinate "C-M 2 O 3 " structure. All of the sesquioxides are basic, and absorb water and carbon dioxide from air to form carbonates, hydroxides and hydroxycarbonates. They dissolve in acids to form salts. Cerium forms
1408-496: A US court rejected General Electric 's attempt to patent it, overturning U.S. patent 1,082,933 granted in 1913 to William D. Coolidge . It is suggested that remnants of wolfram have been found in what may have been the garden of the astronomer/alchemist Tycho Brahe The name tungsten (which means ' heavy stone ' in Swedish and was the old Swedish name for the mineral scheelite and other minerals of similar density)
1584-491: A close packed structure like most of the lanthanides but has an unusual 9 layer repeat Gschneider and Daane (1988) attribute the trend in melting point which increases across the series, ( lanthanum (920 °C) – lutetium (1622 °C)) to the extent of hybridization of the 6s, 5d, and 4f orbitals. The hybridization is believed to be at its greatest for cerium, which has the lowest melting point of all, 795 °C. The lanthanide metals are soft; their hardness increases across
1760-568: A colorless gas. At around 250 °C it will react with chlorine or bromine, and under certain hot conditions will react with iodine. Finely divided tungsten is pyrophoric . The most common formal oxidation state of tungsten is +6, but it exhibits all oxidation states from −2 to +6. Tungsten typically combines with oxygen to form the yellow tungstic oxide , WO 3 , which dissolves in aqueous alkaline solutions to form tungstate ions, WO 4 . Tungsten carbides (W 2 C and WC) are produced by heating powdered tungsten with carbon. W 2 C
1936-528: A component of magnets in hybrid car motors." The global demand for rare-earth elements (REEs) is expected to increase more than fivefold by 2030. The REE geochemical classification is usually done on the basis of their atomic weight . One of the most common classifications divides REE into 3 groups: light rare earths (LREE - from 57 La to 60 Nd), intermediate (MREE - from 62 Sm to 67 Ho) and heavy (HREE - from 68 Er to 71 Lu). REE usually appear as trivalent ions, except for Ce and Eu which can take
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#17330856345442112-453: A deeper (4f) shell is progressively filled with electrons as the atomic number increases from 57 towards 71. For many years, mixtures of more than one rare earth were considered to be single elements, such as neodymium and praseodymium being thought to be the single element didymium. Very small differences in solubility are used in solvent and ion-exchange purification methods for these elements, which require repeated application to obtain
2288-426: A different atom such as phosphorus in place of the two central hydrogens in metatungstate produces a wide variety of heteropoly acids, such as phosphotungstic acid H 3 PW 12 O 40 . Tungsten trioxide can form intercalation compounds with alkali metals. These are known as bronzes ; an example is sodium tungsten bronze . In gaseous form, tungsten forms the diatomic species W 2 . These molecules feature
2464-541: A diverse range of coordination geometries , many of which are irregular, and also manifests itself in the highly fluxional nature of the complexes. As there is no energetic reason to be locked into a single geometry, rapid intramolecular and intermolecular ligand exchange will take place. This typically results in complexes that rapidly fluctuate between all possible configurations. Many of these features make lanthanide complexes effective catalysts . Hard Lewis acids are able to polarise bonds upon coordination and thus alter
2640-656: A few percent of yttrium). Uranium ores from Ontario have occasionally yielded yttrium as a byproduct. Well-known minerals containing cerium, and other LREE, include bastnäsite , monazite , allanite , loparite , ancylite , parisite , lanthanite , chevkinite, cerite , stillwellite , britholite, fluocerite , and cerianite. Monazite (marine sands from Brazil , India , or Australia ; rock from South Africa ), bastnäsite (from Mountain Pass rare earth mine , or several localities in China), and loparite ( Kola Peninsula , Russia ) have been
2816-422: A half-life of (1.8 ± 0.2) × 10 years; on average, this yields about two alpha decays of W per gram of natural tungsten per year. This rate is equivalent to a specific activity of roughly 63 micro- becquerel per kilogram. This rate of decay is orders of magnitude lower than that observed in carbon or potassium as found on earth, which likewise contain small amounts of long-lived radioactive isotopes. Bismuth
2992-614: A high probability of being found close to the nucleus and are thus strongly affected as the nuclear charge increases across the series ; this results in a corresponding decrease in ionic radii referred to as the lanthanide contraction . The low probability of the 4f electrons existing at the outer region of the atom or ion permits little effective overlap between the orbitals of a lanthanide ion and any binding ligand . Thus lanthanide complexes typically have little or no covalent character and are not influenced by orbital geometries. The lack of orbital interaction also means that varying
3168-544: A maximum number of 25 was estimated. The use of X-ray spectra (obtained by X-ray crystallography ) by Henry Gwyn Jeffreys Moseley made it possible to assign atomic numbers to the elements. Moseley found that the exact number of lanthanides had to be 15, but that element 61 had not yet been discovered. (This is promethium, a radioactive element whose most stable isotope has a half-life of just 18 years.) Using these facts about atomic numbers from X-ray crystallography, Moseley also showed that hafnium (element 72) would not be
3344-431: A melt phase if one is present. REE are chemically very similar and have always been difficult to separate, but the gradual decrease in ionic radius from light REE (LREE) to heavy REE (HREE), called the lanthanide contraction , can produce a broad separation between light and heavy REE. The larger ionic radii of LREE make them generally more incompatible than HREE in rock-forming minerals, and will partition more strongly into
3520-401: A melt phase, while HREE may prefer to remain in the crystalline residue, particularly if it contains HREE-compatible minerals like garnet . The result is that all magma formed from partial melting will always have greater concentrations of LREE than HREE, and individual minerals may be dominated by either HREE or LREE, depending on which range of ionic radii best fits the crystal lattice. Among
3696-503: A mine in the village of Ytterby in Sweden ; four of the rare-earth elements bear names derived from this single location. A table listing the 17 rare-earth elements, their atomic number and symbol, the etymology of their names, and their main uses (see also Applications of lanthanides ) is provided here. Some of the rare-earth elements are named after the scientists who discovered them, or elucidated their elemental properties, and some after
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#17330856345443872-466: A mixture of three to all 15 of the lanthanides (along with yttrium as a 16th) occur in minerals, such as monazite and samarskite (for which samarium is named). These minerals can also contain group 3 elements, and actinides such as uranium and thorium. A majority of the rare earths were discovered at the same mine in Ytterby , Sweden and four of them are named (yttrium, ytterbium, erbium, terbium) after
4048-638: A much lower superconducting transition temperature T C relative to the β phase: ca. 0.015 K vs. 1–4 K; mixing the two phases allows obtaining intermediate T C values. The T C value can also be raised by alloying tungsten with another metal (e.g. 7.9 K for W- Tc ). Such tungsten alloys are sometimes used in low-temperature superconducting circuits. Naturally occurring tungsten consists of four stable isotopes ( W, W, W, and W) and one very long-lived radioisotope, W. Theoretically, all five can decay into isotopes of element 72 ( hafnium ) by alpha emission , but only W has been observed to do so, with
4224-477: A purified metal. The diverse applications of refined metals and their compounds can be attributed to the subtle and pronounced variations in their electronic, electrical, optical, and magnetic properties. By way of example of the term meaning "hidden" rather than "scarce", cerium is almost as abundant as copper; on the other hand promethium , with no stable or long-lived isotopes, is truly rare. * Between initial Xe and final 6s electronic shells ** Sm has
4400-411: A quarry in the village of Ytterby , Sweden and termed "rare" because it had never yet been seen. Arrhenius's "ytterbite" reached Johan Gadolin , a Royal Academy of Turku professor, and his analysis yielded an unknown oxide ("earth" in the geological parlance of the day), which he called yttria . Anders Gustav Ekeberg isolated beryllium from the gadolinite but failed to recognize other elements in
4576-530: A range of oxidation states. Notable examples include the trigonal prismatic W(CH 3 ) 6 and octahedral W(CO) 6 . The world's reserves of tungsten are 3,200,000 tonnes; they are mostly located in China (1,800,000 t), Canada (290,000 t), Russia (160,000 t), Vietnam (95,000 t) and Bolivia . As of 2017, China, Vietnam and Russia are the leading suppliers with 79,000, 7,200 and 3,100 tonnes, respectively. Canada had ceased production in late 2015 due to
4752-451: A rare-earth element. Moseley was killed in World War I in 1915, years before hafnium was discovered. Hence, the claim of Georges Urbain that he had discovered element 72 was untrue. Hafnium is an element that lies in the periodic table immediately below zirconium , and hafnium and zirconium have very similar chemical and physical properties. During the 1940s, Frank Spedding and others in
4928-515: A relatively stable +2 oxidation state for Eu and Yb is usually explained by the stability (exchange energy) of half filled (f ) and fully filled f . GdI 2 possesses the layered MoS 2 structure, is ferromagnetic and exhibits colossal magnetoresistance . The sesquihalides Ln 2 X 3 and the Ln 7 I 12 compounds listed in the table contain metal clusters , discrete Ln 6 I 12 clusters in Ln 7 I 12 and condensed clusters forming chains in
5104-400: A rock salt structure. EuO is ferromagnetic at low temperatures, and is a semiconductor with possible applications in spintronics . A mixed Eu /Eu oxide Eu 3 O 4 can be produced by reducing Eu 2 O 3 in a stream of hydrogen. Neodymium and samarium also form monoxides, but these are shiny conducting solids, although the existence of samarium monoxide is considered dubious. All of
5280-403: A separate group of rare-earth elements (the terbium group), or europium was included in the cerium group, and gadolinium and terbium were included in the yttrium group. In the latter case, the f-block elements are split into half: the first half (La–Eu) form the cerium group, and the second half (Gd–Yb) together with group 3 (Sc, Y, Lu) form the yttrium group. The reason for this division arose from
5456-480: A sharp blow. The hardness and heat resistance of tungsten can contribute to useful alloys . A good example is high-speed steel , which can contain as much as 18% tungsten. Tungsten's high melting point makes tungsten a good material for applications like rocket nozzles , for example in the UGM-27 Polaris submarine-launched ballistic missile . Tungsten alloys are used in a wide range of applications, including
Rare-earth element - Misplaced Pages Continue
5632-481: A shortage of tungsten used in the shell core, caused in part by the Wolfram Crisis , limited their use. Tungsten has also been used in dense inert metal explosives , which use it as dense powder to reduce collateral damage while increasing the lethality of explosives within a small radius. Tungsten(IV) sulfide is a high temperature lubricant and is a component of catalysts for hydrodesulfurization . MoS 2
5808-419: A similar effect. In sedimentary rocks, rare-earth elements in clastic sediments are a representation of provenance. The rare-earth element concentrations are not typically affected by sea and river waters, as rare-earth elements are insoluble and thus have very low concentrations in these fluids. As a result, when sediment is transported, rare-earth element concentrations are unaffected by the fluid and instead
5984-591: A stoichiometric dioxide, CeO 2 , where cerium has an oxidation state of +4. CeO 2 is basic and dissolves with difficulty in acid to form Ce solutions, from which Ce salts can be isolated, for example the hydrated nitrate Ce(NO 3 ) 4 .5H 2 O. CeO 2 is used as an oxidation catalyst in catalytic converters. Praseodymium and terbium form non-stoichiometric oxides containing Ln , although more extreme reaction conditions can produce stoichiometric (or near stoichiometric) PrO 2 and TbO 2 . Europium and ytterbium form salt-like monoxides, EuO and YbO, which have
6160-421: A temperature of 400 °C (752 °F). These elements and their compounds have no biological function other than in several specialized enzymes, such as in lanthanide-dependent methanol dehydrogenases in bacteria. The water-soluble compounds are mildly to moderately toxic, but the insoluble ones are not. All isotopes of promethium are radioactive, and it does not occur naturally in the earth's crust, except for
6336-515: A trace amount generated by spontaneous fission of uranium-238 . They are often found in minerals with thorium , and less commonly uranium . Though rare-earth elements are technically relatively plentiful in the entire Earth's crust ( cerium being the 25th-most-abundant element at 68 parts per million, more abundant than copper ), in practice this is spread thin across trace impurities, so to obtain rare earths at usable purity requires processing enormous amounts of raw ore at great expense, thus
6512-499: A tungsten bar with gold, which has been observed since the 1980s, or taking an existing gold bar, drilling holes, and replacing the removed gold with tungsten rods. The densities are not exactly the same, and other properties of gold and tungsten differ, but gold-plated tungsten will pass superficial tests. Gold-plated tungsten is available commercially from China (the main source of tungsten), both in jewelry and as bars. Because it retains its strength at high temperatures and has
6688-457: A valence of 3 and form sesquioxides (cerium forms CeO 2 ). Five different crystal structures are known, depending on the element and the temperature. The X-phase and the H-phase are only stable above 2000 K. At lower temperatures, there are the hexagonal A-phase, the monoclinic B-phase, and the cubic C-phase, which is the stable form at room temperature for most of the elements. The C-phase
6864-490: A well-known IV state, as removing the 4th electron in this case produces a half-full 4f configuration. The additional stable valences for Ce and Eu mean that their abundances in rocks sometimes varies significantly relative to the other rare earth elements: see cerium anomaly and europium anomaly . The similarity in ionic radius between adjacent lanthanide elements makes it difficult to separate them from each other in naturally occurring ores and other mixtures. Historically,
7040-414: Is hypoallergenic , and is harder than gold alloys (though not as hard as tungsten carbide), making it useful for rings that will resist scratching, especially in designs with a brushed finish . Because the density is so similar to that of gold (tungsten is only 0.36% less dense), and its price of the order of one-thousandth, tungsten can also be used in counterfeiting of gold bars , such as by plating
7216-475: Is selective laser melting , which is a form of 3D printing and allows creating complex three-dimensional shapes. Tungsten is mainly used in the production of hard materials based on tungsten carbide (WC), one of the hardest carbides . WC is an efficient electrical conductor , but W 2 C is less so. WC is used to make wear-resistant abrasives , and "carbide" cutting tools such as knives, drills, circular saws , dies , milling and turning tools used by
Rare-earth element - Misplaced Pages Continue
7392-434: Is a chemical element ; it has symbol W and atomic number 74. It is a rare metal found naturally on Earth almost exclusively as compounds with other elements. It was identified as a distinct element in 1781 and first isolated as a metal in 1783. Its important ores include scheelite and wolframite , the latter lending the element its alternative name. The free element is remarkable for its robustness, especially
7568-555: Is a low-lying excited state for La, Ce, and Gd; for Lu, the 4f shell is already full, and the fifteenth electron has no choice but to enter 5d). With the exception of lutetium, the 4f orbitals are chemically active in all lanthanides and produce profound differences between lanthanide chemistry and transition metal chemistry. The 4f orbitals penetrate the [Xe] core and are isolated, and thus they do not participate much in bonding. This explains why crystal field effects are small and why they do not form π bonds. As there are seven 4f orbitals,
7744-539: Is a useful oxidizing agent. The Ce(IV) is the exception owing to the tendency to form an unfilled f shell. Otherwise tetravalent lanthanides are rare. However, recently Tb(IV) and Pr(IV) complexes have been shown to exist. Lanthanide metals react exothermically with hydrogen to form LnH 2 , dihydrides. With the exception of Eu and Yb, which resemble the Ba and Ca hydrides (non-conducting, transparent salt-like compounds), they form black, pyrophoric , conducting compounds where
7920-420: Is added to molten steel to remove oxygen and sulfur, stable oxysulfides are produced that form an immiscible solid. All of the lanthanides form a mononitride, LnN, with the rock salt structure. The mononitrides have attracted interest because of their unusual physical properties. SmN and EuN are reported as being " half metals ". NdN, GdN, TbN and DyN are ferromagnetic, SmN is antiferromagnetic. Applications in
8096-536: Is also sometimes considered a lanthanide, despite being a d-block element and a transition metal. The informal chemical symbol Ln is used in general discussions of lanthanide chemistry to refer to any lanthanide. All but one of the lanthanides are f-block elements, corresponding to the filling of the 4f electron shell . Lutetium is a d-block element (thus also a transition metal ), and on this basis its inclusion has been questioned; however, like its congeners scandium and yttrium in group 3, it behaves similarly to
8272-468: Is also true of transition metals . However, transition metals are able to use vibronic coupling to break this rule. The valence orbitals in lanthanides are almost entirely non-bonding and as such little effective vibronic coupling takes, hence the spectra from f → f transitions are much weaker and narrower than those from d → d transitions. In general this makes the colors of lanthanide complexes far fainter than those of transition metal complexes. Viewing
8448-460: Is called the bixbyite structure, as it occurs in a mineral of that name ( (Mn,Fe) 2 O 3 ). As seen in the chart, rare-earth elements are found on Earth at similar concentrations to many common transition metals. The most abundant rare-earth element is cerium , which is actually the 25th most abundant element in Earth's crust , having 68 parts per million (about as common as copper). The exception
8624-527: Is extracted into kerosene containing tri- n -butylphosphate . The strength of the complexes formed increases as the ionic radius decreases, so solubility in the organic phase increases. Complete separation can be achieved continuously by use of countercurrent exchange methods. The elements can also be separated by ion-exchange chromatography , making use of the fact that the stability constant for formation of EDTA complexes increases for log K ≈ 15.5 for [La(EDTA)] to log K ≈ 19.8 for [Lu(EDTA)] . When in
8800-476: Is heated with hydrogen or carbon to produce powdered tungsten. Because of tungsten's high melting point, it is not commercially feasible to cast tungsten ingots . Instead, powdered tungsten is mixed with small amounts of powdered nickel or other metals, and sintered . During the sintering process, the nickel diffuses into the tungsten, producing an alloy. Tungsten can also be extracted by hydrogen reduction of WF 6 : or pyrolytic decomposition : Tungsten
8976-599: Is high, weathering forms a thick argillized regolith, this process is called supergene enrichment and produces laterite deposits; heavy rare-earth elements are incorporated into the residual clay by absorption. This kind of deposit is only mined for REE in Southern China, where the majority of global heavy rare-earth element production occurs. REE-laterites do form elsewhere, including over the carbonatite at Mount Weld in Australia. REE may also be extracted from placer deposits if
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#17330856345449152-484: Is in tungsten carbide , a wear-resistant metal used in metalworking , mining , and construction . About 50% of tungsten is used in tungsten carbide, with the remaining major use being alloys and steels: less than 10% is used other compounds. Tungsten is the only metal in the third transition series that is known to occur in biomolecules , being found in a few species of bacteria and archaea . However, tungsten interferes with molybdenum and copper metabolism and
9328-488: Is known as the alkaline earth elements for much the same reason. The "rare" in the name "rare earths" has more to do with the difficulty of separating of the individual elements than the scarcity of any of them. By way of the Greek dysprositos for "hard to get at", element 66, dysprosium was similarly named. The elements 57 (La) to 71 (Lu) are very similar chemically to one another and frequently occur together in nature. Often
9504-465: Is more ductile and can be cut with a hard-steel hacksaw . Tungsten occurs in many alloys, which have numerous applications, including incandescent light bulb filaments, X-ray tubes , electrodes in gas tungsten arc welding , superalloys , and radiation shielding . Tungsten's hardness and high density make it suitable for military applications in penetrating projectiles . Tungsten compounds are often used as industrial catalysts . Its largest use
9680-642: Is more commonly used for such applications. Tungsten oxides are used in ceramic glazes and calcium / magnesium tungstates are used widely in fluorescent lighting . Crystal tungstates are used as scintillation detectors in nuclear physics and nuclear medicine . Other salts that contain tungsten are used in the chemical and tanning industries. Tungsten oxide (WO 3 ) is incorporated into selective catalytic reduction (SCR) catalysts found in coal-fired power plants. These catalysts convert nitrogen oxides ( NO x ) to nitrogen (N 2 ) and water (H 2 O) using ammonia (NH 3 ). The tungsten oxide helps with
9856-489: Is not traded as a futures contract and cannot be tracked on exchanges like the London Metal Exchange . The tungsten industry often uses independent pricing references such as Argus Media or Metal Bulletin as a basis for contracts. The prices are usually quoted for tungsten concentrate or WO 3 . Approximately half of the tungsten is consumed for the production of hard materials – namely tungsten carbide – with
10032-414: Is often explained by the poor shielding of the 5s and 5p electrons by the 4f electrons. The chemistry of the lanthanides is dominated by the +3 oxidation state, and in Ln compounds the 6s electrons and (usually) one 4f electron are lost and the ions have the configuration [Xe]4f . All the lanthanide elements exhibit the oxidation state +3. In addition, Ce can lose its single f electron to form Ce with
10208-444: Is possible to observe the serial trend of the REE by reporting their normalized concentrations against the atomic number. The trends that are observed in "spider" diagrams are typically referred to as "patterns", which may be diagnostic of petrological processes that have affected the material of interest. According to the general shape of the patterns or thanks to the presence (or absence) of so-called "anomalies", information regarding
10384-658: Is problematic even in depleted form, or where uranium's additional pyrophoric properties are not desired (for example, in ordinary small arms bullets designed to penetrate body armor). Similarly, tungsten alloys have also been used in shells , grenades , and missiles , to create supersonic shrapnel. Germany used tungsten during World War II to produce shells for anti-tank gun designs using the Gerlich squeeze bore principle to achieve very high muzzle velocity and enhanced armor penetration from comparatively small caliber and light weight field artillery. The weapons were highly effective but
10560-426: Is resistant to chemical attack, although it reacts strongly with chlorine to form tungsten hexachloride (WCl 6 ). In aqueous solution, tungstate gives the heteropoly acids and polyoxometalate anions under neutral and acidic conditions. As tungstate is progressively treated with acid, it first yields the soluble, metastable "paratungstate A" anion , W 7 O 24 , which over time converts to
10736-450: Is somewhat toxic to most forms of animal life. In its raw form, tungsten is a hard steel-grey metal that is often brittle and hard to work . Purified, monocrystalline tungsten retains its hardness (which exceeds that of many steels), and becomes malleable enough that it can be worked easily. It is worked by forging , drawing , or extruding but it is more commonly formed by sintering . Of all metals in pure form, tungsten has
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#173308563454410912-616: Is strictly regulated by the Chinese Government, which fights illegal mining and excessive pollution originating from mining and refining processes. There is a large deposit of tungsten ore on the edge of Dartmoor in the United Kingdom , which was exploited during World War I and World War II as the Hemerdon Mine . Following increases in tungsten prices, this mine was reactivated in 2014, but ceased activities in 2018. Within
11088-729: Is suggested. The resistivities of the lanthanide metals are relatively high, ranging from 29 to 134 μΩ·cm. These values can be compared to a good conductor such as aluminium, which has a resistivity of 2.655 μΩ·cm. With the exceptions of La, Yb, and Lu (which have no unpaired f electrons), the lanthanides are strongly paramagnetic, and this is reflected in their magnetic susceptibilities. Gadolinium becomes ferromagnetic at below 16 °C ( Curie point ). The other heavier lanthanides – terbium, dysprosium, holmium, erbium, thulium, and ytterbium – become ferromagnetic at much lower temperatures. 4f * Not including initial [Xe] core f → f transitions are symmetry forbidden (or Laporte-forbidden), which
11264-443: Is synthetically produced in nuclear reactors. Due to their chemical similarity, the concentrations of rare earths in rocks are only slowly changed by geochemical processes, making their proportions useful for geochronology and dating fossils. Rare-earth elements occur in nature in combination with phosphate ( monazite ), carbonate - fluoride ( bastnäsite ), and oxygen anions. In their oxides, most rare-earth elements only have
11440-465: Is the highest of the lanthanides. The sum of the first two ionization energies for ytterbium are the second lowest in the series and its third ionization energy is the second highest. The high third ionization energy for Eu and Yb correlate with the half filling 4f and complete filling 4f of the 4f subshell, and the stability afforded by such configurations due to exchange energy. Europium and ytterbium form salt like compounds with Eu and Yb , for example
11616-516: Is the highly unstable and radioactive promethium "rare earth" is quite scarce. The longest-lived isotope of promethium has a half-life of 17.7 years, so the element exists in nature in only negligible amounts (approximately 572 g in the entire Earth's crust). Promethium is one of the two elements that do not have stable (non-radioactive) isotopes and are followed by (i.e. with higher atomic number) stable elements (the other being technetium ). The rare-earth elements are often found together. During
11792-539: Is used in English, French, and many other languages as the name of the element, but wolfram (or volfram ) is used in most European (especially Germanic and Slavic) languages and is derived from the mineral wolframite , which is the origin of the chemical symbol W . The name wolframite is derived from German wolf rahm ( ' wolf soot, wolf cream ' ), the name given to tungsten by Johan Gottschalk Wallerius in 1747. This, in turn, derives from Latin lupi spuma ,
11968-695: The Carrock mine from the German owned Cumbrian Mining Company and, during World War I , restrict German access elsewhere. In World War II , tungsten played a more significant role in background political dealings. Portugal, as the main European source of the element, was put under pressure from both sides , because of its deposits of wolframite ore at Panasqueira . Tungsten's desirable properties such as resistance to high temperatures, its hardness and density, and its strengthening of alloys made it an important raw material for
12144-579: The EU , the Austrian Felbertal scheelite deposit is one of the few producing tungsten mines. Portugal is one of Europe's main tungsten producers, with 121 kt of contained tungsten in mineral concentrates from 1910 to 2020, accounting for roughly 3.3% of the global production. Tungsten is considered to be a conflict mineral due to the unethical mining practices observed in the Democratic Republic of
12320-562: The Oddo–Harkins rule : even-numbered REE at abundances of about 5% each, and odd-numbered REE at abundances of about 1% each. Similar compositions are found in xenotime or gadolinite. Well-known minerals containing yttrium, and other HREE, include gadolinite, xenotime, samarskite , euxenite , fergusonite , yttrotantalite, yttrotungstite, yttrofluorite (a variety of fluorite ), thalenite, and yttrialite . Small amounts occur in zircon , which derives its typical yellow fluorescence from some of
12496-483: The upper mantle (200 to 600 km depth). This melt becomes enriched in incompatible elements, like the rare-earth elements, by leaching them out of the crystalline residue. The resultant magma rises as a diapir , or diatreme , along pre-existing fractures, and can be emplaced deep in the crust , or erupted at the surface. Typical REE enriched deposits types forming in rift settings are carbonatites, and A- and M-Type granitoids. Near subduction zones, partial melting of
12672-428: The "heavy" group from 6.965 (ytterbium) to 9.32 (thulium), as well as including yttrium at 4.47. Europium has a density of 5.24. Rare-earth elements, except scandium , are heavier than iron and thus are produced by supernova nucleosynthesis or by the s-process in asymptotic giant branch stars. In nature, spontaneous fission of uranium-238 produces trace amounts of radioactive promethium , but most promethium
12848-567: The 4 f orbital which acts against the electrons of the 6 s and 5 d orbitals. The lanthanide contraction has a direct effect on the geochemistry of the lanthanides, which show a different behaviour depending on the systems and processes in which they are involved. The effect of the lanthanide contraction can be observed in the REE behaviour both in a CHARAC-type geochemical system (CHArge-and-RAdius-Controlled) where elements with similar charge and radius should show coherent geochemical behaviour, and in non-CHARAC systems, such as aqueous solutions, where
13024-469: The Congo . South Korea's Sangdong mine , one of the world's largest tungsten mines with 7,890,000 tonnes of high-grade tungsten reportedly buried, was closed in 1994 due to low profitability but has since re-registered mining rights and is scheduled to resume activities in 2024. Tungsten is extracted from its ores in several stages. The ore is eventually converted to tungsten(VI) oxide (WO 3 ), which
13200-411: The Greek λανθανειν ( lanthanein ), "to lie hidden". Rather than referring to their natural abundance, the word reflects their property of "hiding" behind each other in minerals. The term derives from lanthanum , first discovered in 1838, at that time a so-called new rare-earth element "lying hidden" or "escaping notice" in a cerium mineral, and it is an irony that lanthanum was later identified as
13376-498: The LREE. This has economic consequences: large ore bodies of LREE are known around the world and are being exploited. Ore bodies for HREE are more rare, smaller, and less concentrated. Most of the current supply of HREE originates in the "ion-absorption clay" ores of Southern China. Some versions provide concentrates containing about 65% yttrium oxide, with the HREE being present in ratios reflecting
13552-515: The United States (during the Manhattan Project ) developed chemical ion-exchange procedures for separating and purifying rare-earth elements. This method was first applied to the actinides for separating plutonium-239 and neptunium from uranium , thorium , actinium , and the other actinides in the materials produced in nuclear reactors . Plutonium-239 was very desirable because it is
13728-449: The accompanying HREE. The zirconium mineral eudialyte , such as is found in southern Greenland , contains small but potentially useful amounts of yttrium. Of the above yttrium minerals, most played a part in providing research quantities of lanthanides during the discovery days. Xenotime is occasionally recovered as a byproduct of heavy-sand processing, but is not as abundant as the similarly recovered monazite (which typically contains
13904-417: The aerospace and automotive industries and radiation shielding. Superalloys containing tungsten, such as Hastelloy and Stellite , are used in turbine blades and wear-resistant parts and coatings. Tungsten's heat resistance makes it useful in arc welding applications when combined with another highly-conductive metal such as silver or copper. The silver or copper provides the necessary conductivity and
14080-496: The anhydrous rare-earth phosphates, it is the tetragonal mineral xenotime that incorporates yttrium and the HREE, whereas the monoclinic monazite phase incorporates cerium and the LREE preferentially. The smaller size of the HREE allows greater solid solubility in the rock-forming minerals that make up Earth's mantle, and thus yttrium and the HREE show less enrichment in Earth's crust relative to chondritic abundance than does cerium and
14256-422: The arms industry, both as a constituent of weapons and equipment and employed in production itself, e.g., in tungsten carbide cutting tools for machining steel. Now tungsten is used in many more applications such as aircraft and motorsport ballast weights, darts, anti-vibration tooling, and sporting equipment. Tungsten is unique amongst the elements in that it has been the subject of patent proceedings. In 1928,
14432-448: The closure of its sole tungsten mine. Meanwhile, Vietnam had significantly increased its output in the 2010s, owing to the major optimization of its domestic refining operations, and overtook Russia and Bolivia. China remains the world's leader not only in production, but also in export and consumption of tungsten products. Tungsten production is gradually increasing outside China because of the rising demand. Meanwhile, its supply by China
14608-853: The core of igneous complexes; they consist of fine-grained calcite and hematite, sometimes with significant concentrations of ankerite and minor concentrations of siderite. Large carbonatite deposits enriched in rare-earth elements include Mount Weld in Australia, Thor Lake in Canada, Zandkopsdrift in South Africa, and Mountain Pass in the USA. Peralkaline granites (A-Type granitoids) have very high concentrations of alkaline elements and very low concentrations of phosphorus; they are deposited at moderate depths in extensional zones, often as igneous ring complexes, or as pipes, massive bodies, and lenses. These fluids have very low viscosities and high element mobility, which allows for
14784-408: The crude yttria and found the same substances that Mosander obtained, but Berlin named (1860) the substance giving pink salts erbium , and Delafontaine named the substance with the yellow peroxide terbium . This confusion led to several false claims of new elements, such as the mosandrium of J. Lawrence Smith , or the philippium and decipium of Delafontaine. Due to the difficulty in separating
14960-731: The crystallization of large grains, despite a relatively short crystallization time upon emplacement; their large grain size is why these deposits are commonly referred to as pegmatites. Economically viable pegmatites are divided into Lithium-Cesium-Tantalum (LCT) and Niobium-Yttrium-Fluorine (NYF) types; NYF types are enriched in rare-earth minerals. Examples of rare-earth pegmatite deposits include Strange Lake in Canada and Khaladean-Buregtey in Mongolia. Nepheline syenite (M-Type granitoids) deposits are 90% feldspar and feldspathoid minerals. They are deposited in small, circular massifs and contain high concentrations of rare-earth-bearing accessory minerals . For
15136-404: The density, tungsten is seen as an alternative (albeit more expensive) to lead fishing sinkers . Depleted uranium is also used for these purposes, due to similarly high density. Seventy-five-kg blocks of tungsten were used as "cruise balance mass devices" on the entry vehicle portion of the 2012 Mars Science Laboratory spacecraft. It is an ideal material to use as a dolly for riveting , where
15312-412: The difference in solubility of rare-earth double sulfates with sodium and potassium. The sodium double sulfates of the cerium group are poorly soluble, those of the terbium group slightly, and those of the yttrium group are very soluble. Sometimes, the yttrium group was further split into the erbium group (dysprosium, holmium, erbium, and thulium) and the ytterbium group (ytterbium and lutetium), but today
15488-445: The diiodides have relatively short metal-metal separations. The CuTi 2 structure of the lanthanum, cerium and praseodymium diiodides along with HP-NdI 2 contain 4 nets of metal and iodine atoms with short metal-metal bonds (393-386 La-Pr). these compounds should be considered to be two-dimensional metals (two-dimensional in the same way that graphite is). The salt-like dihalides include those of Eu, Dy, Tm, and Yb. The formation of
15664-407: The electron structure is also an important parameter to consider as the lanthanide contraction affects the ionic potential . A direct consequence is that, during the formation of coordination bonds, the REE behaviour gradually changes along the series. Furthermore, the lanthanide contraction causes the ionic radius of Ho (0.901 Å) to be almost identical to that of Y (0.9 Å), justifying the inclusion of
15840-474: The electrophilicity of compounds, with a classic example being the Luche reduction . The large size of the ions coupled with their labile ionic bonding allows even bulky coordinating species to bind and dissociate rapidly, resulting in very high turnover rates; thus excellent yields can often be achieved with loadings of only a few mol%. The lack of orbital interactions combined with the lanthanide contraction means that
16016-651: The element showing the anomaly and the predictable one based on the average of the normalized concentrations of the two elements in the previous and next position in the series, according to the equation: where [ REE i ] n {\displaystyle [{\text{REE}}_{i}]_{n}} is the normalized concentration of the element whose anomaly has to be calculated, [ REE i − 1 ] n {\displaystyle [{\text{REE}}_{i-1}]_{n}} and [ REE i + 1 ] n {\displaystyle [{\text{REE}}_{i+1}]_{n}}
16192-488: The element tungsten is not ferromagnetic (but iron is), when it is present in steel in these proportions, it stabilizes the martensite phase, which has greater ferromagnetism than the ferrite (iron) phase due to its greater resistance to magnetic domain wall motion . Tungsten, usually alloyed with nickel , iron , or cobalt to form heavy alloys, is used in kinetic energy penetrators as an alternative to depleted uranium , in applications where uranium's radioactivity
16368-485: The elements or (with the exception of Eu 2 S 3 ) sulfidizing the oxide (Ln 2 O 3 ) with H 2 S. The sesquisulfides, Ln 2 S 3 generally lose sulfur when heated and can form a range of compositions between Ln 2 S 3 and Ln 3 S 4 . The sesquisulfides are insulators but some of the Ln 3 S 4 are metallic conductors (e.g. Ce 3 S 4 ) formulated (Ln ) 3 (S ) 4 (e ), while others (e.g. Eu 3 S 4 and Sm 3 S 4 ) are semiconductors. Structurally
16544-417: The existence of an unknown element. The fractional crystallization of the oxides then yielded europium in 1901. In 1839 the third source for rare earths became available. This is a mineral similar to gadolinite called uranotantalum (now called " samarskite ") an oxide of a mixture of elements such as yttrium, ytterbium, iron, uranium, thorium, calcium, niobium, and tantalum. This mineral from Miass in
16720-563: The fact that it has the highest melting point of all known elements, melting at 3,422 °C (6,192 °F; 3,695 K). It also has the highest boiling point , at 5,930 °C (10,706 °F; 6,203 K). Its density is 19.254 g/cm , comparable with that of uranium and gold , and much higher (about 1.7 times) than that of lead . Polycrystalline tungsten is an intrinsically brittle and hard material (under standard conditions, when uncombined), making it difficult to work into metal . However, pure single-crystalline tungsten
16896-405: The field of spintronics are being investigated. CeN is unusual as it is a metallic conductor, contrasting with the other nitrides also with the other cerium pnictides. A simple description is Ce N (e–) but the interatomic distances are a better match for the trivalent state rather than for the tetravalent state. A number of different explanations have been offered. The nitrides can be prepared by
17072-649: The first in an entire series of chemically similar elements and gave its name to the whole series. Together with the stable elements of group 3, scandium , yttrium , and lutetium , the trivial name " rare earths " is sometimes used to describe the set of lanthanides. The "earth" in the name "rare earths" arises from the minerals from which they were isolated, which were uncommon oxide-type minerals. However, these elements are neither rare in abundance nor "earths" (an obsolete term for water-insoluble strongly basic oxides of electropositive metals incapable of being smelted into metal using late 18th century technology). Group 2
17248-511: The following observations apply: anomalies in europium are dominated by the crystallization of feldspars . Hornblende , controls the enrichment of MREE compared to LREE and HREE. Depletion of LREE relative to HREE may be due to the crystallization of olivine , orthopyroxene , and clinopyroxene . On the other hand, the depletion of HREE relative to LREE may be due to the presence of garnet , as garnet preferentially incorporates HREE into its crystal structure. The presence of zircon may also cause
17424-470: The form of coordination complexes , lanthanides exist overwhelmingly in their +3 oxidation state , although particularly stable 4f configurations can also give +4 (Ce, Pr, Tb) or +2 (Sm, Eu, Yb) ions. All of these forms are strongly electropositive and thus lanthanide ions are hard Lewis acids . The oxidation states are also very stable; with the exceptions of SmI 2 and cerium(IV) salts , lanthanides are not used for redox chemistry. 4f electrons have
17600-431: The form of Ce and Eu depending on the redox conditions of the system. Consequentially, REE are characterized by a substantial identity in their chemical reactivity, which results in a serial behaviour during geochemical processes rather than being characteristic of a single element of the series. Sc, Y, and Lu can be electronically distinguished from the other rare earths because they do not have f valence electrons, whereas
17776-565: The fractionation of trace elements (including rare-earth elements) into the liquid phase (the melt/magma) into the solid phase (the mineral). If an element preferentially remains in the solid phase it is termed 'compatible', and if it preferentially partitions into the melt phase it is described as 'incompatible'. Each element has a different partition coefficient, and therefore fractionates into solid and liquid phases distinctly. These concepts are also applicable to metamorphic and sedimentary petrology. In igneous rocks, particularly in felsic melts,
17952-442: The gas phase the trihalides are planar or approximately planar, the lighter lanthanides have a lower % of dimers, the heavier lanthanides a higher proportion. The dimers have a similar structure to Al 2 Cl 6 . Some of the dihalides are conducting while the rest are insulators. The conducting forms can be considered as Ln electride compounds where the electron is delocalised into a conduction band, Ln (X ) 2 (e ). All of
18128-404: The geographical locations where discovered. A mnemonic for the names of the sixth-row elements in order is "Lately college parties never produce sexy European girls that drink heavily even though you look". Rare earths were mainly discovered as components of minerals. Ytterbium was found in the "ytterbite" (renamed to gadolinite in 1800) discovered by Lieutenant Carl Axel Arrhenius in 1787 at
18304-446: The heavy rare-earth elements (HREE), and those that fall in between are typically referred to as the middle rare-earth elements (MREE). Commonly, rare-earth elements with atomic numbers 57 to 61 (lanthanum to promethium) are classified as light and those with atomic numbers 62 and greater are classified as heavy rare-earth elements. Increasing atomic numbers between light and heavy rare-earth elements and decreasing atomic radii throughout
18480-492: The high wear resistance and thermal conductivity of tungsten carbide improves the printing of abrasive filaments. Some string instrument strings incorporates tungsten. Tungsten is used as an absorber on the electron telescope on the Cosmic Ray System of the two Voyager spacecraft . Its density, similar to that of gold, allows tungsten to be used in jewelry as an alternative to gold or platinum . Metallic tungsten
18656-515: The highest melting point (3,422 °C, 6,192 °F), lowest vapor pressure (at temperatures above 1,650 °C, 3,000 °F), and the highest tensile strength . Although carbon remains solid at higher temperatures than tungsten, carbon sublimes at atmospheric pressure instead of melting, so it has no melting point. Moreover, tungsten's most stable crystal phase does not exhibit any high-pressure-induced structural transformations for pressures up to at least 364 gigapascals. Tungsten has
18832-419: The iodides form soluble complexes with ethers, e.g. TmI 2 (dimethoxyethane) 3 . Samarium(II) iodide is a useful reducing agent. Ln(II) complexes can be synthesized by transmetalation reactions. The normal range of oxidation states can be expanded via the use of sterically bulky cyclopentadienyl ligands , in this way many lanthanides can be isolated as Ln(II) compounds. Ce(IV) in ceric ammonium nitrate
19008-574: The laboratory and there are currently few examples them being used on an industrial scale. Lanthanides exist in many forms other than coordination complexes and many of these are industrially useful. In particular lanthanide metal oxides are used as heterogeneous catalysts in various industrial processes. The trivalent lanthanides mostly form ionic salts. The trivalent ions are hard acceptors and form more stable complexes with oxygen-donor ligands than with nitrogen-donor ligands. The larger ions are 9-coordinate in aqueous solution, [Ln(H 2 O) 9 ] but
19184-419: The lanthanides can be compared with aluminium. In aluminium the sum of the first three ionization energies is 5139 kJ·mol , whereas the lanthanides fall in the range 3455 – 4186 kJ·mol . This correlates with the highly reactive nature of the lanthanides. The sum of the first two ionization energies for europium, 1632 kJ·mol can be compared with that of barium 1468.1 kJ·mol and europium's third ionization energy
19360-409: The lanthanides change in size across the series but that their chemistry remains much the same. This allows for easy tuning of the steric environments and examples exist where this has been used to improve the catalytic activity of the complex and change the nuclearity of metal clusters. Despite this, the use of lanthanide coordination complexes as homogeneous catalysts is largely restricted to
19536-416: The lanthanides form hydroxides, Ln(OH) 3 . With the exception of lutetium hydroxide, which has a cubic structure, they have the hexagonal UCl 3 structure. The hydroxides can be precipitated from solutions of Ln . They can also be formed by the reaction of the sesquioxide, Ln 2 O 3 , with water, but although this reaction is thermodynamically favorable it is kinetically slow for the heavier members of
19712-510: The lanthanides form monochalcogenides, LnQ, (Q= S, Se, Te). The majority of the monochalcogenides are conducting, indicating a formulation Ln Q (e-) where the electron is in conduction bands. The exceptions are SmQ, EuQ and YbQ which are semiconductors or insulators but exhibit a pressure induced transition to a conducting state. Compounds LnQ 2 are known but these do not contain Ln but are Ln compounds containing polychalcogenide anions. Oxysulfides Ln 2 O 2 S are well known, they all have
19888-401: The lanthanides from left to right in the periodic table, the seven 4f atomic orbitals become progressively more filled (see above and Periodic table § Electron configuration table ). The electronic configuration of most neutral gas-phase lanthanide atoms is [Xe]6s 4f , where n is 56 less than the atomic number Z . Exceptions are La, Ce, Gd, and Lu, which have 4f 5d (though even then 4f
20064-470: The latter among the REE. The application of rare-earth elements to geology is important to understanding the petrological processes of igneous , sedimentary and metamorphic rock formation. In geochemistry , rare-earth elements can be used to infer the petrological mechanisms that have affected a rock due to the subtle atomic size differences between the elements, which causes preferential fractionation of some rare earths relative to others depending on
20240-476: The less soluble "paratungstate B" anion, H 2 W 12 O 42 . Further acidification produces the very soluble metatungstate anion, H 2 W 12 O 40 , after which equilibrium is reached. The metatungstate ion exists as a symmetric cluster of twelve tungsten- oxygen octahedra known as the Keggin anion. Many other polyoxometalate anions exist as metastable species. The inclusion of
20416-418: The logarithm to the base 10 of the value. Commonly, the rare-earth elements are normalized to chondritic meteorites , as these are believed to be the closest representation of unfractionated Solar System material. However, other normalizing standards can be applied depending on the purpose of the study. Normalization to a standard reference value, especially of a material believed to be unfractionated, allows
20592-402: The lowest coefficient of thermal expansion of any pure metal. The low thermal expansion and high melting point and tensile strength of tungsten originate from strong covalent bonds formed between tungsten atoms by the 5d electrons. Alloying small quantities of tungsten with steel greatly increases its toughness . Tungsten exists in two major crystalline forms: α and β. The former has
20768-470: The main grouping is between the cerium and the yttrium groups. Today, the rare-earth elements are classified as light or heavy rare-earth elements, rather than in cerium and yttrium groups. The classification of rare-earth elements is inconsistent between authors. The most common distinction between rare-earth elements is made by atomic numbers ; those with low atomic numbers are referred to as light rare-earth elements (LREE), those with high atomic numbers are
20944-535: The mass necessary for good results can be achieved in a compact bar. High-density alloys of tungsten with nickel, copper or iron are used in high-quality darts (to allow for a smaller diameter and thus tighter groupings) or for artificial flies (tungsten beads allow the fly to sink rapidly). Tungsten is also used as a heavy bolt to lower the rate of fire of the SWD M11/9 sub-machine gun from 1300 RPM to 700 RPM. Tungsten has seen use recently in nozzles for 3D printing ;
21120-431: The metal matrix in place of cobalt because it takes a higher luster when polished. Sometimes manufacturers or retailers refer to tungsten carbide as a metal, but it is a ceramic . Because of tungsten carbide's hardness, rings made of this material are extremely abrasion resistant, and will hold a burnished finish longer than rings made of metallic tungsten. Tungsten carbide rings are brittle, however, and may crack under
21296-438: The metal sub-lattice is face centred cubic and the H atoms occupy tetrahedral sites. Further hydrogenation produces a trihydride which is non-stoichiometric , non-conducting, more salt like. The formation of trihydride is associated with and increase in 8–10% volume and this is linked to greater localization of charge on the hydrogen atoms which become more anionic (H hydride anion) in character. The only tetrahalides known are
21472-431: The metal typically has little effect on the complex (other than size), especially when compared to transition metals . Complexes are held together by weaker electrostatic forces which are omni-directional and thus the ligands alone dictate the symmetry and coordination of complexes. Steric factors therefore dominate, with coordinative saturation of the metal being balanced against inter-ligand repulsion. This results in
21648-519: The metals (and determining the separation is complete), the total number of false discoveries was dozens, with some putting the total number of discoveries at over a hundred. There were no further discoveries for 30 years, and the element didymium was listed in the periodic table of elements with a molecular mass of 138. In 1879, Delafontaine used the new physical process of optical flame spectroscopy and found several new spectral lines in didymia. Also in 1879, Paul Émile Lecoq de Boisbaudran isolated
21824-535: The metalworking, woodworking, mining , petroleum and construction industries. Carbide tooling is actually a ceramic/metal composite, where metallic cobalt acts as a binding (matrix) material to hold the WC particles in place. This type of industrial use accounts for about 60% of current tungsten consumption. The jewelry industry makes rings of sintered tungsten carbide , tungsten carbide/metal composites, and also metallic tungsten. WC/metal composite rings use nickel as
22000-687: The most part, these deposits are small but important examples include Illimaussaq-Kvanefeld in Greenland, and Lovozera in Russia. Rare-earth elements can also be enriched in deposits by secondary alteration either by interactions with hydrothermal fluids or meteoric water or by erosion and transport of resistate REE-bearing minerals. Argillization of primary minerals enriches insoluble elements by leaching out silica and other soluble elements, recrystallizing feldspar into clay minerals such kaolinite, halloysite, and montmorillonite. In tropical regions where precipitation
22176-483: The most stable being W ( t 1/2 6.4 minutes). Tungsten is a mostly non-reactive element: it does not react with water, is immune to attack by most acids and bases, and does not react with oxygen or air at room temperature. At elevated temperatures (i.e., when red-hot) it reacts with oxygen to form the trioxide compound tungsten(VI), WO 3 . It will, however, react directly with fluorine (F 2 ) at room temperature to form tungsten(VI) fluoride (WF 6 ),
22352-412: The most stable of which are W with a half-life of 121.2 days, W with a half-life of 75.1 days, W with a half-life of 69.4 days, W with a half-life of 21.6 days, and W with a half-life of 23.72 h. All of the remaining radioactive isotopes have half-lives of less than 3 hours, and most of these have half-lives below 8 minutes. Tungsten also has 11 meta states , with
22528-714: The name Georg Agricola used for the mineral in 1546, which translates into English as ' wolf's froth ' and is a reference to the large amounts of tin consumed by the mineral during its extraction, as though the mineral devoured it like a wolf. This naming follows a tradition of colorful names miners from the Ore Mountains would give various minerals, out of a superstition that certain ones that looked as if they contained then-known valuable metals but when extracted were somehow "hexed". Cobalt (cf. Kobold ), pitchblende (cf. German blenden for ' to blind, to deceive ' ) and nickel (cf. "Old Nick") derive their names from
22704-414: The name "rare" earths. Because of their geochemical properties, rare-earth elements are typically dispersed and not often found concentrated in rare-earth minerals . Consequently, economically exploitable ore deposits are sparse. The first rare-earth mineral discovered (1787) was gadolinite , a black mineral composed of cerium, yttrium, iron, silicon, and other elements. This mineral was extracted from
22880-560: The new element samarium from the mineral samarskite . The samaria earth was further separated by Lecoq de Boisbaudran in 1886, and a similar result was obtained by Jean Charles Galissard de Marignac by direct isolation from samarskite. They named the element gadolinium after Johan Gadolin , and its oxide was named " gadolinia ". Further spectroscopic analysis between 1886 and 1901 of samaria, yttria, and samarskite by William Crookes , Lecoq de Boisbaudran and Eugène-Anatole Demarçay yielded several new spectral lines that indicated
23056-423: The normalized concentration, [ REE i ] sam {\displaystyle {[{\text{REE}}_{i}]_{\text{sam}}}} the analytical concentration of the element measured in the sample, and [ REE i ] ref {\displaystyle {[{\text{REE}}_{i}]_{\text{ref}}}} the concentration of the same element in the reference material. It
23232-426: The normalized concentrations of the respectively previous and next elements along the series. The rare-earth elements patterns observed in igneous rocks are primarily a function of the chemistry of the source where the rock came from, as well as the fractionation history the rock has undergone. Fractionation is in turn a function of the partition coefficients of each element. Partition coefficients are responsible for
23408-419: The number of unpaired electrons can be as high as 7, which gives rise to the large magnetic moments observed for lanthanide compounds. Measuring the magnetic moment can be used to investigate the 4f electron configuration, and this is a useful tool in providing an insight into the chemical bonding. The lanthanide contraction , i.e. the reduction in size of the Ln ion from La (103 pm) to Lu (86.1 pm),
23584-432: The observed abundances to be compared to the initial abundances of the element. Normalization also removes the pronounced 'zig-zag' pattern caused by the differences in abundance between even and odd atomic numbers . Normalization is carried out by dividing the analytical concentrations of each element of the series by the concentration of the same element in a given standard, according to the equation: where n indicates
23760-516: The ore. After this discovery in 1794, a mineral from Bastnäs near Riddarhyttan , Sweden, which was believed to be an iron – tungsten mineral, was re-examined by Jöns Jacob Berzelius and Wilhelm Hisinger . In 1803 they obtained a white oxide and called it ceria . Martin Heinrich Klaproth independently discovered the same oxide and called it ochroia . It took another 30 years for researchers to determine that other elements were contained in
23936-406: The other 14. The term rare-earth element or rare-earth metal is often used to include the stable group 3 elements Sc, Y, and Lu in addition to the 4f elements. All lanthanide elements form trivalent cations, Ln , whose chemistry is largely determined by the ionic radius , which decreases steadily from lanthanum (La) to lutetium (Lu). These elements are called lanthanides because the elements in
24112-414: The others do, but the chemical behaviour is almost the same. A distinguishing factor in the geochemical behaviour of the REE is linked to the so-called " lanthanide contraction " which represents a higher-than-expected decrease in the atomic/ionic radius of the elements along the series. This is determined by the variation of the shielding effect towards the nuclear charge due to the progressive filling of
24288-426: The pervasiveness of the chromium(III) compounds. The highest oxidation state is seen in tungsten(VI) oxide (WO 3 ). Tungsten(VI) oxide is soluble in aqueous base , forming tungstate (WO 4 ). This oxyanion condenses at lower pH values, forming polyoxotungstates . The broad range of oxidation states of tungsten is reflected in its various chlorides: Organotungsten compounds are numerous and also span
24464-619: The physical strength of the catalyst and extends catalyst life. Tungsten containing catalysts are promising for epoxidation, oxidation, and hydrogenolysis reactions. Tungsten heteropoly acids are key component of multifunctional catalysts. Tungstates can be used as photocatalyst, while the tungsten sulfide as electrocatalyst. Applications requiring its high density include weights, counterweights , ballast keels for yachts, tail ballast for commercial aircraft, rotor weights for civil and military helicopters, and as ballast in race cars for NASCAR and Formula One . Being slightly less than twice
24640-487: The polymorphic form. The colors of the γ-sesquisulfides are La 2 S 3 , white/yellow; Ce 2 S 3 , dark red; Pr 2 S 3 , green; Nd 2 S 3 , light green; Gd 2 S 3 , sand; Tb 2 S 3 , light yellow and Dy 2 S 3 , orange. The shade of γ-Ce 2 S 3 can be varied by doping with Na or Ca with hues ranging from dark red to yellow, and Ce 2 S 3 based pigments are used commercially and are seen as low toxicity substitutes for cadmium based pigments. All of
24816-444: The principal ores of cerium and the light lanthanides. Enriched deposits of rare-earth elements at the surface of the Earth, carbonatites and pegmatites , are related to alkaline plutonism , an uncommon kind of magmatism that occurs in tectonic settings where there is rifting or that are near subduction zones. In a rift setting, the alkaline magma is produced by very small degrees of partial melting (<1%) of garnet peridotite in
24992-440: The processes at work. The geochemical study of the REE is not carried out on absolute concentrations – as it is usually done with other chemical elements – but on normalized concentrations in order to observe their serial behaviour. In geochemistry, rare-earth elements are typically presented in normalized "spider" diagrams, in which concentration of rare-earth elements are normalized to a reference standard and are then expressed as
25168-419: The rare-earth elements relatively expensive. Their industrial use was very limited until efficient separation techniques were developed, such as ion exchange , fractional crystallization, and liquid–liquid extraction during the late 1950s and early 1960s. Some ilmenite concentrates contain small amounts of scandium and other rare-earth elements, which could be analysed by X-ray fluorescence (XRF). Before
25344-532: The reaction of lanthanum metals with nitrogen. Some nitride is produced along with the oxide, when lanthanum metals are ignited in air. Alternative methods of synthesis are a high temperature reaction of lanthanide metals with ammonia or the decomposition of lanthanide amides, Ln(NH 2 ) 3 . Achieving pure stoichiometric compounds, and crystals with low defect density has proved difficult. The lanthanide nitrides are sensitive to air and hydrolyse producing ammonia. Tungsten Tungsten (also called wolfram )
25520-402: The remaining major use being in alloys and steels. Less than 10% is used in other chemical compounds . Because of the high ductile-brittle transition temperature of tungsten, its products are conventionally manufactured through powder metallurgy , spark plasma sintering , chemical vapor deposition , hot isostatic pressing , and thermoplastic routes. A more flexible manufacturing alternative
25696-434: The rock retains the rare-earth element concentration from its source. Lanthanide The lanthanide ( / ˈ l æ n θ ə n aɪ d / ) or lanthanoid ( / ˈ l æ n θ ə n ɔɪ d / ) series of chemical elements comprises at least the 14 metallic chemical elements with atomic numbers 57–70, from lanthanum through ytterbium . In the periodic table, they fill the 4f orbitals. Lutetium (element 71)
25872-459: The salt like dihydrides. Both europium and ytterbium dissolve in liquid ammonia forming solutions of Ln (NH 3 ) x again demonstrating their similarities to the alkaline earth metals. The relative ease with which the 4th electron can be removed in cerium and (to a lesser extent praseodymium) indicates why Ce(IV) and Pr(IV) compounds can be formed, for example CeO 2 is formed rather than Ce 2 O 3 when cerium reacts with oxygen. Also Tb has
26048-481: The same ore deposits as the lanthanides and exhibit similar chemical properties, but have different electrical and magnetic properties . The term 'rare-earth' is a misnomer because they are not actually scarce, although historically it took a long time to isolate these elements. These metals tarnish slowly in air at room temperature and react slowly with cold water to form hydroxides, liberating hydrogen. They react with steam to form oxides and ignite spontaneously at
26224-1044: The same miners' idiom. Tungsten has thus far not been found in nature in its pure form. Instead, tungsten is found mainly in the minerals wolframite and scheelite . Wolframite is iron – manganese tungstate (Fe,Mn)WO 4 , a solid solution of the two minerals ferberite (FeWO 4 ) and hübnerite (MnWO 4 ), while scheelite is calcium tungstate (CaWO 4 ). Other tungsten minerals range in their level of abundance from moderate to very rare, and have almost no economic value. Tungsten forms chemical compounds in oxidation states from -II to VI. Higher oxidation states, always as oxides, are relevant to its terrestrial occurrence and its biological roles, mid-level oxidation states are often associated with metal clusters , and very low oxidation states are typically associated with CO complexes . The chemistries of tungsten and molybdenum show strong similarities to each other, as well as contrasts with their lighter congener, chromium . The relative rarity of tungsten(III), for example, contrasts with
26400-406: The same structure with 7-coordinate Ln atoms, and 3 sulfur and 4 oxygen atoms as near neighbours. Doping these with other lanthanide elements produces phosphors. As an example, gadolinium oxysulfide , Gd 2 O 2 S doped with Tb produces visible photons when irradiated with high energy X-rays and is used as a scintillator in flat panel detectors. When mischmetal , an alloy of lanthanide metals,
26576-624: The seafloor, bit by bit, over tens of millions of years. One square patch of metal-rich mud 2.3 kilometers wide might contain enough rare earths to meet most of the global demand for a year, Japanese geologists report in Nature Geoscience ." "I believe that rare[-]earth resources undersea are much more promising than on-land resources," said Kato. "[C]oncentrations of rare earths were comparable to those found in clays mined in China. Some deposits contained twice as much heavy rare earths such as dysprosium,
26752-486: The sedimentary parent lithology contains REE-bearing, heavy resistate minerals. In 2011, Yasuhiro Kato, a geologist at the University of Tokyo who led a study of Pacific Ocean seabed mud, published results indicating the mud could hold rich concentrations of rare-earth minerals. The deposits, studied at 78 sites, came from "[h]ot plumes from hydrothermal vents pull[ing] these materials out of seawater and deposit[ing] them on
26928-417: The sequential accretion of the Earth, the dense rare-earth elements were incorporated into the deeper portions of the planet. Early differentiation of molten material largely incorporated the rare earths into mantle rocks. The high field strength and large ionic radii of rare earths make them incompatible with the crystal lattices of most rock-forming minerals, so REE will undergo strong partitioning into
27104-476: The series are chemically similar to lanthanum . Because "lanthanide" means "like lanthanum", it has been argued that lanthanum cannot logically be a lanthanide, but the International Union of Pure and Applied Chemistry (IUPAC) acknowledges its inclusion based on common usage. In presentations of the periodic table , the f-block elements are customarily shown as two additional rows below the main body of
27280-491: The series causes chemical variations. Europium is exempt of this classification as it has two valence states: Eu and Eu. Yttrium is grouped as heavy rare-earth element due to chemical similarities. The break between the two groups is sometimes put elsewhere, such as between elements 63 (europium) and 64 (gadolinium). The actual metallic densities of these two groups overlap, with the "light" group having densities from 6.145 (lanthanum) to 7.26 (promethium) or 7.52 (samarium) g/cc, and
27456-418: The series. Fajans' rules indicate that the smaller Ln ions will be more polarizing and their salts correspondingly less ionic. The hydroxides of the heavier lanthanides become less basic, for example Yb(OH) 3 and Lu(OH) 3 are still basic hydroxides but will dissolve in hot concentrated NaOH . All of the lanthanides form Ln 2 Q 3 (Q= S, Se, Te). The sesquisulfides can be produced by reaction of
27632-408: The series. Europium stands out, as it has the lowest density in the series at 5.24 g/cm and the largest metallic radius in the series at 208.4 pm. It can be compared to barium, which has a metallic radius of 222 pm. It is believed that the metal contains the larger Eu ion and that there are only two electrons in the conduction band. Ytterbium also has a large metallic radius, and a similar explanation
27808-438: The sesquihalides. Scandium forms a similar cluster compound with chlorine, Sc 7 Cl 12 Unlike many transition metal clusters these lanthanide clusters do not have strong metal-metal interactions and this is due to the low number of valence electrons involved, but instead are stabilised by the surrounding halogen atoms. LaI and TmI are the only known monohalides. LaI, prepared from the reaction of LaI 3 and La metal, it has
27984-415: The sesquisulfides adopt structures that vary according to the size of the Ln metal. The lighter and larger lanthanides favoring 7-coordinate metal atoms, the heaviest and smallest lanthanides (Yb and Lu) favoring 6 coordination and the rest structures with a mixture of 6 and 7 coordination. Polymorphism is common amongst the sesquisulfides. The colors of the sesquisulfides vary metal to metal and depend on
28160-407: The smaller ions are 8-coordinate, [Ln(H 2 O) 8 ] . There is some evidence that the later lanthanides have more water molecules in the second coordination sphere. Complexation with monodentate ligands is generally weak because it is difficult to displace water molecules from the first coordination sphere. Stronger complexes are formed with chelating ligands because of the chelate effect , such as
28336-401: The southern Ural Mountains was documented by Gustav Rose . The Russian chemist R. Harmann proposed that a new element he called " ilmenium " should be present in this mineral, but later, Christian Wilhelm Blomstrand , Galissard de Marignac, and Heinrich Rose found only tantalum and niobium ( columbium ) in it. The exact number of rare-earth elements that existed was highly unclear, and
28512-575: The stable electronic configuration of xenon. Also, Eu can gain an electron to form Eu with the f configuration that has the extra stability of a half-filled shell. Other than Ce(IV) and Eu(II), none of the lanthanides are stable in oxidation states other than +3 in aqueous solution. In terms of reduction potentials, the Ln couples are nearly the same for all lanthanides, ranging from −1.99 (for Eu) to −2.35 V (for Pr). Thus these metals are highly reducing, with reducing power similar to alkaline earth metals such as Mg (−2.36 V). The ionization energies for
28688-763: The subducting plate within the asthenosphere (80 to 200 km depth) produces a volatile-rich magma (high concentrations of CO 2 and water), with high concentrations of alkaline elements, and high element mobility that the rare earths are strongly partitioned into. This melt may also rise along pre-existing fractures, and be emplaced in the crust above the subducting slab or erupted at the surface. REE-enriched deposits forming from these melts are typically S-Type granitoids. Alkaline magmas enriched with rare-earth elements include carbonatites, peralkaline granites (pegmatites), and nepheline syenite . Carbonatites crystallize from CO 2 -rich fluids, which can be produced by partial melting of hydrous-carbonated lherzolite to produce
28864-399: The system under examination and the occurring geochemical processes can be obtained. The anomalies represent enrichment (positive anomalies) or depletion (negative anomalies) of specific elements along the series and are graphically recognizable as positive or negative "peaks" along the REE patterns. The anomalies can be numerically quantified as the ratio between the normalized concentration of
29040-400: The table. This convention is entirely a matter of aesthetics and formatting practicality; a rarely used wide-formatted periodic table inserts the 4f and 5f series in their proper places, as parts of the table's sixth and seventh rows (periods), respectively. The 1985 IUPAC "Red Book" (p. 45) recommends using lanthanoid instead of lanthanide , as the ending -ide normally indicates
29216-517: The tetra-anion derived from 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid ( DOTA ). The most common divalent derivatives of the lanthanides are for Eu(II), which achieves a favorable f configuration. Divalent halide derivatives are known for all of the lanthanides. They are either conventional salts or are Ln(III) " electride "-like salts. The simple salts include YbI 2 , EuI 2 , and SmI 2 . The electride-like salts, described as Ln , 2I , e , include LaI 2 , CeI 2 and GdI 2 . Many of
29392-590: The tetrafluorides of cerium , praseodymium , terbium , neodymium and dysprosium, the last two known only under matrix isolation conditions. All of the lanthanides form trihalides with fluorine, chlorine, bromine and iodine. They are all high melting and predominantly ionic in nature. The fluorides are only slightly soluble in water and are not sensitive to air, and this contrasts with the other halides which are air sensitive, readily soluble in water and react at high temperature to form oxohalides. The trihalides were important as pure metal can be prepared from them. In
29568-479: The time that ion exchange methods and elution were available, the separation of the rare earths was primarily achieved by repeated precipitation or crystallization . In those days, the first separation was into two main groups, the cerium earths (lanthanum, cerium, praseodymium, neodymium, and samarium) and the yttrium earths (scandium, yttrium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium). Europium, gadolinium, and terbium were either considered as
29744-441: The tungsten allows the welding rod to withstand the high temperatures of the arc welding environment. Quenched (martensitic) tungsten steel (approx. 5.5% to 7.0% W with 0.5% to 0.7% C) was used for making hard permanent magnets, due to its high remanence and coercivity , as noted by John Hopkinson (1849–1898) as early as 1886. The magnetic properties of a metal or an alloy are very sensitive to microstructure. For example, while
29920-484: The two ores ceria and yttria (the similarity of the rare-earth metals' chemical properties made their separation difficult). In 1839 Carl Gustav Mosander , an assistant of Berzelius, separated ceria by heating the nitrate and dissolving the product in nitric acid . He called the oxide of the soluble salt lanthana . It took him three more years to separate the lanthana further into didymia and pure lanthana. Didymia, although not further separable by Mosander's techniques,
30096-492: The very laborious processes of cascading and fractional crystallization were used. Because the lanthanide ions have slightly different radii, the lattice energy of their salts and hydration energies of the ions will be slightly different, leading to a small difference in solubility . Salts of the formula Ln(NO 3 ) 3 ·2NH 4 NO 3 ·4H 2 O can be used. Industrially, the elements are separated from each other by solvent extraction . Typically an aqueous solution of nitrates
30272-483: The village and a fifth (holmium) after Stockholm; scandium is named after Scandinavia , thulium after the old name Thule , and the immediately-following group 4 element (number 72) hafnium is named for the Latin name of the city of Copenhagen . The properties of the lanthanides arise from the order in which the electron shells of these elements are filled—the outermost (6s) has the same configuration for all of them, and
30448-481: Was identical to tungstic acid. Later that year, at the Royal Basque Society in the town of Bergara , Spain, the brothers succeeded in isolating tungsten by reduction of this acid with charcoal , and they are credited with the discovery of the element (they called it "wolfram" or "volfram"). The strategic value of tungsten came to notice in the early 20th century. British authorities acted in 1912 to free
30624-492: Was in fact still a mixture of oxides. In 1842 Mosander also separated the yttria into three oxides: pure yttria, terbia, and erbia (all the names are derived from the town name "Ytterby"). The earth giving pink salts he called terbium ; the one that yielded yellow peroxide he called erbium . In 1842 the number of known rare-earth elements had reached six: yttrium, cerium, lanthanum, didymium, erbium, and terbium. Nils Johan Berlin and Marc Delafontaine tried also to separate
30800-585: Was long thought to be non-radioactive, but Bi (its longest lived isotope) actually decays with a half life of 2.01 × 10 years or about a factor 10 slower than W . However, due to naturally occurring bismuth being 100% Bi , its specific activity is actually higher than that of natural tungsten at 3 milli-becquerel per kilogram. The other naturally occurring isotopes of tungsten have not been observed to decay, constraining their half-lives to be at least 4 × 10 years . Another 34 artificial radioisotopes of tungsten have been characterized,
30976-493: Was once thought to be in space group I 2 1 3 (no. 199), but is now known to be in space group Ia 3 (no. 206). The structure is similar to that of fluorite or cerium dioxide (in which the cations form a face-centred cubic lattice and the anions sit inside the tetrahedra of cations), except that one-quarter of the anions (oxygen) are missing. The unit cell of these sesquioxides corresponds to eight unit cells of fluorite or cerium dioxide, with 32 cations instead of 4. This
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