Scandium | ||||||||||||||||||||||||||||||||||||||||||||||
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Pronunciation | /ˈskændiəm/ | |||||||||||||||||||||||||||||||||||||||||||||
Appearance | silvery white | |||||||||||||||||||||||||||||||||||||||||||||
Standard atomic weight Ar°(Sc) | ||||||||||||||||||||||||||||||||||||||||||||||
Scandium in the periodic table | ||||||||||||||||||||||||||||||||||||||||||||||
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Atomic number (Z) | 21 | |||||||||||||||||||||||||||||||||||||||||||||
Group | group 3 | |||||||||||||||||||||||||||||||||||||||||||||
Period | period 4 | |||||||||||||||||||||||||||||||||||||||||||||
Block | d-block | |||||||||||||||||||||||||||||||||||||||||||||
Electron configuration | [ Ar ] 3d1 4s2 | |||||||||||||||||||||||||||||||||||||||||||||
Electrons per shell | 2, 8, 9, 2 | |||||||||||||||||||||||||||||||||||||||||||||
Physical properties | ||||||||||||||||||||||||||||||||||||||||||||||
Phase at STP | solid | |||||||||||||||||||||||||||||||||||||||||||||
Melting point | 1814 K (1541 °C,2806 °F) | |||||||||||||||||||||||||||||||||||||||||||||
Boiling point | 3109 K(2836 °C,5136 °F) | |||||||||||||||||||||||||||||||||||||||||||||
Density (at 20° C) | 2.989 g/cm3 [3] | |||||||||||||||||||||||||||||||||||||||||||||
when liquid (at m.p.) | 2.80 g/cm3 | |||||||||||||||||||||||||||||||||||||||||||||
Heat of fusion | 14.1 kJ/mol | |||||||||||||||||||||||||||||||||||||||||||||
Heat of vaporization | 332.7 kJ/mol | |||||||||||||||||||||||||||||||||||||||||||||
Molar heat capacity | 25.52 J/(mol·K) | |||||||||||||||||||||||||||||||||||||||||||||
Vapor pressure
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Atomic properties | ||||||||||||||||||||||||||||||||||||||||||||||
Oxidation states | common: +3 0, [4] +1, [5] +2 [6] | |||||||||||||||||||||||||||||||||||||||||||||
Electronegativity | Pauling scale: 1.36 | |||||||||||||||||||||||||||||||||||||||||||||
Ionization energies |
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Atomic radius | empirical:162 pm | |||||||||||||||||||||||||||||||||||||||||||||
Covalent radius | 170±7 pm | |||||||||||||||||||||||||||||||||||||||||||||
Van der Waals radius | 211 pm | |||||||||||||||||||||||||||||||||||||||||||||
Spectral lines of scandium | ||||||||||||||||||||||||||||||||||||||||||||||
Other properties | ||||||||||||||||||||||||||||||||||||||||||||||
Natural occurrence | primordial | |||||||||||||||||||||||||||||||||||||||||||||
Crystal structure | hexagonal close-packed (hcp)(hP2) | |||||||||||||||||||||||||||||||||||||||||||||
Lattice constants | a = 330.89 pm c = 526.80 pm (at 20 °C) [3] | |||||||||||||||||||||||||||||||||||||||||||||
Thermal expansion | 9.97×10−6/K (at 20 °C) [a] | |||||||||||||||||||||||||||||||||||||||||||||
Thermal conductivity | 15.8 W/(m⋅K) | |||||||||||||||||||||||||||||||||||||||||||||
Electrical resistivity | α, poly: 562 nΩ⋅m(at r.t., calculated) | |||||||||||||||||||||||||||||||||||||||||||||
Magnetic ordering | paramagnetic | |||||||||||||||||||||||||||||||||||||||||||||
Molar magnetic susceptibility | +315.0×10−6 cm3/mol(292 K) [7] | |||||||||||||||||||||||||||||||||||||||||||||
Young's modulus | 74.4 GPa | |||||||||||||||||||||||||||||||||||||||||||||
Shear modulus | 29.1 GPa | |||||||||||||||||||||||||||||||||||||||||||||
Bulk modulus | 56.6 GPa | |||||||||||||||||||||||||||||||||||||||||||||
Poisson ratio | 0.279 | |||||||||||||||||||||||||||||||||||||||||||||
Brinell hardness | 736–1200 MPa | |||||||||||||||||||||||||||||||||||||||||||||
CAS Number | 7440-20-2 | |||||||||||||||||||||||||||||||||||||||||||||
History | ||||||||||||||||||||||||||||||||||||||||||||||
Naming | after Scandinavia | |||||||||||||||||||||||||||||||||||||||||||||
Prediction | Dmitri Mendeleev (1871) | |||||||||||||||||||||||||||||||||||||||||||||
Discovery and first isolation | Lars Fredrik Nilson (1879) | |||||||||||||||||||||||||||||||||||||||||||||
Isotopes of scandium | ||||||||||||||||||||||||||||||||||||||||||||||
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Scandium is a chemical element with the symbol Sc and atomic number 21. It is a silvery-white metallic d-block element. Historically, it has been classified as a rare-earth element, [9] together with yttrium and the lanthanides. It was discovered in 1879 by spectral analysis of the minerals euxenite and gadolinite from Scandinavia. [10]
Scandium is present in most of the deposits of rare-earth and uranium compounds, but it is extracted from these ores in only a few mines worldwide. Because of the low availability and difficulties in the preparation of metallic scandium, which was first done in 1937, applications for scandium were not developed until the 1970s, when the positive effects of scandium on aluminium alloys were discovered. Its use in such alloys remains its only major application. The global trade of scandium oxide is 15–20 tonnes per year. [11]
The properties of scandium compounds are intermediate between those of aluminium and yttrium. A diagonal relationship exists between the behavior of magnesium and scandium, just as there is between beryllium and aluminium. In the chemical compounds of the elements in group 3, the predominant oxidation state is +3.
Scandium is a soft metal with a silvery appearance. It develops a slightly yellowish or pinkish cast when oxidized by air. It is susceptible to weathering and dissolves slowly in most dilute acids. It does not react with a 1:1 mixture of nitric acid (HNO3) and 48.0% hydrofluoric acid (HF), possibly due to the formation of an impermeable passive layer. Scandium turnings ignite in the air with a brilliant yellow flame to form scandium oxide. [12]
In nature, scandium is found exclusively as the isotope 45Sc, which has a nuclear spin of 7⁄2; this is its only stable isotope. [13]
The known isotopes of scandium range from 37Sc to 62Sc. [8] The most stable radioisotope is 46Sc, which has a half-life of 83.8 days. Others are 47Sc, 3.35 days; the positron emitter 44Sc, 4 hours; and 48Sc, 43.7 hours. All of the remaining radioactive isotopes have half-lives less than 4 hours, and the majority of them have half-lives less than 2 minutes. The low mass isotopes are very difficult to create. [13] The initial detection of 37Sc and 38Sc only resulted in the characterization of their mass excess. [14] [15] Scandium also has five nuclear isomers: the most stable of these is 44m2Sc (t1/2 = 58.6 h). [16]
The primary decay mode of ground-state scandium isotopes at masses lower than the only stable isotope, 45Sc, is electron capture (or positron emission), but the lightest isotopes (37Sc to 39Sc) undergo proton emission instead, all three of these producing calcium isotopes. The primary decay mode at masses above 45Sc is beta emission, producing titanium isotopes. [8]
In Earth's crust, scandium is not rare. Estimates vary from 18 to 25 ppm, which is comparable to the abundance of cobalt (20–30 ppm). Scandium is only the 50th most common element on Earth (35th most abundant element in the crust), but it is the 23rd most common element in the Sun [17] and the 26th most abundant element in the stars. [18] However, scandium is distributed sparsely and occurs in trace amounts in many minerals. [19] Rare minerals from Scandinavia [20] and Madagascar [21] such as thortveitite, euxenite, and gadolinite are the only known concentrated sources of this element. Thortveitite can contain up to 45% of scandium in the form of scandium oxide. [20]
The stable form of scandium is created in supernovas via the r-process. [22] Also, scandium is created by cosmic ray spallation of the more abundant iron nuclei.
The world production of scandium is in the order of 15–20 tonnes per year, in the form of scandium oxide. The demand is slightly higher, [23] and both the production and demand keep increasing. In 2003, only three mines produced scandium: the uranium and iron mines in Zhovti Vody in Ukraine, the rare-earth mines in Bayan Obo, China, and the apatite mines in the Kola Peninsula, Russia.[ citation needed ] Since then, many other countries have built scandium-producing facilities, including 5 tonnes/year (7.5 tonnes/year Sc2O3) by Nickel Asia Corporation and Sumitomo Metal Mining in the Philippines. [24] [25] In the United States, NioCorp Development hopes[ when? ] to raise $1 billion [26] toward opening a niobium mine at its Elk Creek site in southeast Nebraska, [27] which may be able to produce as much as 95 tonnes of scandium oxide annually. [28] In each case, scandium is a byproduct of the extraction of other elements and is sold as scandium oxide. [29] [30] [31]
To produce metallic scandium, the oxide is converted to scandium fluoride and then reduced with metallic calcium. [32]
Madagascar and the Iveland-Evje region in Norway have the only deposits of minerals with high scandium content, thortveitite (Sc,Y)2(Si2O7), but these are not being exploited. [30] The mineral kolbeckite ScPO4·2H2O has a very high scandium content but is not available in any larger deposits. [30]
The absence of reliable, secure, stable, long-term production has limited the commercial applications of scandium. Despite this low level of use, scandium offers significant benefits. Particularly promising is the strengthening of aluminium alloys with as little as 0.5% scandium. [33] Scandium-stabilized zirconia enjoys a growing market demand for use as a high-efficiency electrolyte in solid oxide fuel cells.
The USGS reports that, from 2015 to 2019 in the US, the price of small quantities of scandium ingot has been $107 to $134 per gram, and that of scandium oxide $4 to $5 per gram. [34]
Scandium chemistry is almost completely dominated by the trivalent ion, Sc3+. The radii of M3+ ions in the table below indicate that the chemical properties of scandium ions have more in common with yttrium ions than with aluminium ions. In part because of this similarity, scandium is often classified as a lanthanide-like element. [35]
The oxide Sc
2O
3 and the hydroxide Sc(OH)
3 are amphoteric: [36]
α- and γ-ScOOH are isostructural with their aluminium hydroxide oxide counterparts. [37] Solutions of Sc3+
in water are acidic due to hydrolysis.
The halides ScX3, where X= Cl, Br, or I, are very soluble in water, but ScF3 is insoluble. In all four halides, the scandium is 6-coordinated. The halides are Lewis acids; for example, ScF3 dissolves in a solution containing excess fluoride ion to form [ScF6]3−. The coordination number 6 is typical for Sc(III). In the larger Y3+ and La3+ ions, coordination numbers of 8 and 9 are common. Scandium triflate is sometimes used as a Lewis acid catalyst in organic chemistry. [38]
Scandium forms a series of organometallic compounds with cyclopentadienyl ligands (Cp), similar to the behavior of the lanthanides. One example is the chlorine-bridged dimer, [ScCp2Cl]2 and related derivatives of pentamethylcyclopentadienyl ligands. [39]
Compounds that feature scandium in oxidation states other than +3 are rare but well characterized. The blue-black compound CsScCl3 is one of the simplest. This material adopts a sheet-like structure that exhibits extensive bonding between the scandium(II) centers. [40] Scandium hydride is not well understood, although it appears not to be a saline hydride of Sc(II). [6] As is observed for most elements, a diatomic scandium hydride has been observed spectroscopically at high temperatures in the gas phase. [5] Scandium borides and carbides are non-stoichiometric, as is typical for neighboring elements. [41]
Lower oxidation states (+2, +1, 0) have also been observed in organoscandium compounds. [42] [4] [43] [44]
Dmitri Mendeleev, who is referred to as the father of the periodic table, predicted the existence of an element ekaboron , with an atomic mass between 40 and 48 in 1869. Lars Fredrik Nilson and his team detected this element in the minerals euxenite and gadolinite in 1879. Nilson prepared 2 grams of scandium oxide of high purity. [45] [46] He named the element scandium, from the Latin Scandia meaning "Scandinavia". Nilson was apparently unaware of Mendeleev's prediction, but Per Teodor Cleve recognized the correspondence and notified Mendeleev. [47] [48]
Metallic scandium was produced for the first time in 1937 by electrolysis of a eutectic mixture of potassium, lithium, and scandium chlorides, at 700–800 °C. [49] The first pound of 99% pure scandium metal was produced in 1960. Production of aluminium alloys began in 1971, following a US patent. [50] Aluminium-scandium alloys were also developed in the USSR. [51]
Laser crystals of gadolinium-scandium-gallium garnet (GSGG) were used in strategic defense applications developed for the Strategic Defense Initiative (SDI) in the 1980s and 1990s. [52] [53]
The main application of scandium by weight is in aluminium-scandium alloys for minor aerospace industry components. These alloys contain between 0.1% and 0.5% of scandium. They were used in Russian military aircraft, specifically the Mikoyan-Gurevich MiG-21 and MiG-29. [54]
The addition of scandium to aluminium limits the grain growth in the heat zone of welded aluminium components. This has two beneficial effects: the precipitated Al3Sc forms smaller crystals than in other aluminium alloys, [54] and the volume of precipitate-free zones at the grain boundaries of age-hardening aluminium alloys is reduced. [54] The Al3Sc precipitate is a coherent precipitate that strengthens the aluminum matrix by applying elastic strain fields that inhibit dislocation movement (i.e., plastic deformation). Al3Sc has an equilibrium L12 superlattice structure exclusive to this system. [55] A fine dispersion of nano scale precipitate can be achieved via heat treatment that can also strengthen the alloys through order hardening. [56] Recent developments include the additions of transition metals such as zirconium (Zr) and rare earth metals like erbium (Er) produce shells surrounding the spherical Al3Sc precipitate that reduce coarsening. [57] These shells are dictated by the diffusivity of the alloying element and lower the cost of the alloy due to less Sc being substituted in part by Zr while maintaining stability and less Sc being needed to form the precipitate. [58] These have made Al3Sc somewhat competitive with titanium alloys along with a wide array of applications. However, titanium alloys, which are similar in lightness and strength, are cheaper and much more widely used. [59]
The alloy Al20Li20Mg10Sc20Ti30 is as strong as titanium, light as aluminium, and hard as some ceramics. [60]
Some items of sports equipment, which rely on lightweight high-performance materials, have been made with scandium-aluminium alloys, including baseball bats, [61] tent poles and bicycle frames and components. [62] Lacrosse sticks are also made with scandium. The American firearm manufacturing company Smith & Wesson produces semi-automatic pistols and revolvers with frames of scandium alloy and cylinders of titanium or carbon steel. [63] [64]
Since 2013, Apworks GmbH, a spin-off of Airbus, have marketed a high strength Scandium containing aluminium alloy processed using metal 3D-Printing (Laser Powder Bed Fusion) under the trademark Scalmalloy which claims very high strength & ductility. [65]
The first scandium-based metal-halide lamps were patented by General Electric and made in North America, although they are now produced in all major industrialized countries. Approximately 20 kg of scandium (as Sc2 O 3) is used annually in the United States for high-intensity discharge lamps. [66] One type of metal-halide lamp, similar to the mercury-vapor lamp, is made from scandium triiodide and sodium iodide. This lamp is a white-light source with high color rendering index that sufficiently resembles sunlight to allow good color-reproduction with TV cameras. [67] About 80 kg of scandium is used in metal-halide lamps/light bulbs globally per year. [68]
Dentists use erbium-chromium-doped yttrium-scandium-gallium garnet (Er,Cr:YSGG) lasers for cavity preparation and in endodontics. [69]
The radioactive isotope 46Sc is used in oil refineries as a tracing agent. [66] Scandium triflate is a catalytic Lewis acid used in organic chemistry. [70]
The 12.4 keV nuclear transition of 45Sc has been studied as a reference for timekeeping applications, with a theoretical precision as much as three orders of magnitude better than the current caesium reference clocks. [71]
Scandium has been proposed for use in solid oxide fuel cells (SOFCs) as a dopant in the electrolyte material, typically zirconia (ZrO₂). [72] Scandium oxide (Sc₂O₃) is one of several possible additives to enhance the ionic conductivity of the zirconia, improving the overall thermal stability, performance and efficiency of the fuel cell. [73] This application would be particularly valuable in clean energy technologies, as SOFCs can utilize a variety of fuels and have high energy conversion efficiencies. [74]
Elemental scandium is considered non-toxic, though extensive animal testing of scandium compounds has not been done. [75] The median lethal dose (LD50) levels for scandium chloride for rats have been determined as 755 mg/kg for intraperitoneal and 4 g/kg for oral administration. [76] In the light of these results, compounds of scandium should be handled as compounds of moderate toxicity. Scandium appears to be handled by the body in a manner similar to gallium, with similar hazards involving its poorly soluble hydroxide. [77]
Barium is a chemical element; it has symbol Ba and atomic number 56. It is the fifth element in group 2 and is a soft, silvery alkaline earth metal. Because of its high chemical reactivity, barium is never found in nature as a free element.
Dysprosium is a chemical element; it has symbol Dy and atomic number 66. It is a rare-earth element in the lanthanide series with a metallic silver luster. Dysprosium is never found in nature as a free element, though, like other lanthanides, it is found in various minerals, such as xenotime. Naturally occurring dysprosium is composed of seven isotopes, the most abundant of which is 164Dy.
Europium is a chemical element; it has symbol Eu and atomic number 63. Europium is a silvery-white metal of the lanthanide series that reacts readily with air to form a dark oxide coating. It is the most chemically reactive, least dense, and softest of the lanthanide elements. It is soft enough to be cut with a knife. Europium was isolated in 1901 and named after the continent of Europe. Europium usually assumes the oxidation state +3, like other members of the lanthanide series, but compounds having oxidation state +2 are also common. All europium compounds with oxidation state +2 are slightly reducing. Europium has no significant biological role and is relatively non-toxic compared to other heavy metals. Most applications of europium exploit the phosphorescence of europium compounds. Europium is one of the rarest of the rare-earth elements on Earth.
Erbium is a chemical element; it has symbol Er and atomic number 68. A silvery-white solid metal when artificially isolated, natural erbium is always found in chemical combination with other elements. It is a lanthanide, a rare-earth element, originally found in the gadolinite mine in Ytterby, Sweden, which is the source of the element's name.
Gadolinium is a chemical element; it has symbol Gd and atomic number 64. Gadolinium is a silvery-white metal when oxidation is removed. It is a malleable and ductile rare-earth element. Gadolinium reacts with atmospheric oxygen or moisture slowly to form a black coating. Gadolinium below its Curie point of 20 °C (68 °F) is ferromagnetic, with an attraction to a magnetic field higher than that of nickel. Above this temperature it is the most paramagnetic element. It is found in nature only in an oxidized form. When separated, it usually has impurities of the other rare earths because of their similar chemical properties.
Lanthanum is a chemical element with the symbol La and the atomic number 57. It is a soft, ductile, silvery-white metal that tarnishes slowly when exposed to air. It is the eponym of the lanthanide series, a group of 15 similar elements between lanthanum and lutetium in the periodic table, of which lanthanum is the first and the prototype. Lanthanum is traditionally counted among the rare earth elements. Like most other rare earth elements, its usual oxidation state is +3, although some compounds are known with an oxidation state of +2. Lanthanum has no biological role in humans but is essential to some bacteria. It is not particularly toxic to humans but does show some antimicrobial activity.
Lutetium is a chemical element; it has symbol Lu and atomic number 71. It is a silvery white metal, which resists corrosion in dry air, but not in moist air. Lutetium is the last element in the lanthanide series, and it is traditionally counted among the rare earth elements; it can also be classified as the first element of the 6th-period transition metals.
Neodymium is a chemical element; it has symbol Nd and atomic number 60. It is the fourth member of the lanthanide series and is considered to be one of the rare-earth metals. It is a hard, slightly malleable, silvery metal that quickly tarnishes in air and moisture. When oxidized, neodymium reacts quickly producing pink, purple/blue and yellow compounds in the +2, +3 and +4 oxidation states. It is generally regarded as having one of the most complex spectra of the elements. Neodymium was discovered in 1885 by the Austrian chemist Carl Auer von Welsbach, who also discovered praseodymium. It is present in significant quantities in the minerals monazite and bastnäsite. Neodymium is not found naturally in metallic form or unmixed with other lanthanides, and it is usually refined for general use. Neodymium is fairly common—about as common as cobalt, nickel, or copper—and is widely distributed in the Earth's crust. Most of the world's commercial neodymium is mined in China, as is the case with many other rare-earth metals.
Terbium is a chemical element; it has the symbol Tb and atomic number 65. It is a silvery-white, rare earth metal that is malleable and ductile. The ninth member of the lanthanide series, terbium is a fairly electropositive metal that reacts with water, evolving hydrogen gas. Terbium is never found in nature as a free element, but it is contained in many minerals, including cerite, gadolinite, monazite, xenotime and euxenite.
Thulium is a chemical element; it has symbol Tm and atomic number 69. It is the thirteenth element in the lanthanide series of metals. It is the second-least abundant lanthanide in the Earth's crust, after radioactively unstable promethium. It is an easily workable metal with a bright silvery-gray luster. It is fairly soft and slowly tarnishes in air. Despite its high price and rarity, thulium is used as a dopant in solid-state lasers, and as the radiation source in some portable X-ray devices. It has no significant biological role and is not particularly toxic.
Zirconium is a chemical element; it has symbol Zr and atomic number 40. First identified in 1789, isolated in impure form in 1824, and manufactured at scale by 1925, pure zirconium is a lustrous transition metal with a greyish-white color that closely resembles hafnium and, to a lesser extent, titanium. It is solid at room temperature, ductile, malleable and corrosion-resistant. The name zirconium is derived from the name of the mineral zircon, the most important source of zirconium. The word is related to Persian zargun. Besides zircon, zirconium occurs in over 140 other minerals, including baddeleyite and eudialyte; most zirconium is produced as a byproduct of minerals mined for titanium and tin.
The alkaline earth metals are six chemical elements in group 2 of the periodic table. They are beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). The elements have very similar properties: they are all shiny, silvery-white, somewhat reactive metals at standard temperature and pressure.
A period 5 element is one of the chemical elements in the fifth row of the periodic table of the chemical elements. The periodic table is laid out in rows to illustrate recurring (periodic) trends in the chemical behaviour of the elements as their atomic number increases: a new row is begun when chemical behaviour begins to repeat, meaning that elements with similar behaviour fall into the same vertical columns. The fifth period contains 18 elements, beginning with rubidium and ending with xenon. As a rule, period 5 elements fill their 5s shells first, then their 4d, and 5p shells, in that order; however, there are exceptions, such as rhodium.
Praseodymium is a chemical element; it has symbol Pr and the atomic number 59. It is the third member of the lanthanide series and is considered one of the rare-earth metals. It is a soft, silvery, malleable and ductile metal, valued for its magnetic, electrical, chemical, and optical properties. It is too reactive to be found in native form, and pure praseodymium metal slowly develops a green oxide coating when exposed to air.
Group 3 is the first group of transition metals in the periodic table. This group is closely related to the rare-earth elements. It contains the four elements scandium (Sc), yttrium (Y), lutetium (Lu), and lawrencium (Lr). The group is also called the scandium group or scandium family after its lightest member.
Yttrium is a chemical element; it has symbol Y and atomic number 39. It is a silvery-metallic transition metal chemically similar to the lanthanides and has often been classified as a "rare-earth element". Yttrium is almost always found in combination with lanthanide elements in rare-earth minerals and is never found in nature as a free element. 89Y is the only stable isotope and the only isotope found in the Earth's crust.
Cerium is a chemical element; it has symbol Ce and atomic number 58. It is a soft, ductile, and silvery-white metal that tarnishes when exposed to air. Cerium is the second element in the lanthanide series, and while it often shows the oxidation state of +3 characteristic of the series, it also has a stable +4 state that does not oxidize water. It is considered one of the rare-earth elements. Cerium has no known biological role in humans but is not particularly toxic, except with intense or continued exposure.
Scandium compounds are compounds containing the element scandium. The chemistry of scandium is almost completely dominated by the trivalent ion, Sc3+, due to its electron configuration, [Ar] 3d14s2. The radii of M3+ ions in the table below indicate that the chemical properties of scandium ions have more in common with yttrium ions than with aluminium ions. In part because of this similarity, scandium is often classified as a lanthanide-like element.
An yttrium compound is a chemical compound containing yttrium. Among these compounds, yttrium generally has a +3 valence. The solubility properties of yttrium compounds are similar to those of the lanthanides. For example oxalates and carbonates are hardly soluble in water, but soluble in excess oxalate or carbonate solutions as complexes are formed. Sulfates and double sulfates are generally soluble. They resemble the "yttrium group" of heavy lanthanide elements.
Aluminium–scandium alloys (AlSc) are aluminum alloys that consist largely of aluminium (Al) and traces of scandium (Sc) as the main alloying elements. In principle, aluminium alloys strengthened with additions of scandium are very similar to traditional nickel-base superalloys in that both are strengthened by coherent, coarsening resistant precipitates with an ordered L12 structure. But Al–Sc alloys contain a much lower volume fraction of precipitates, and the inter-precipitate distance is much smaller than in their nickel-base counterparts. In both cases however, the coarsening resistant precipitates allow the alloys to retain their strength at high temperatures.