Scandium is a
chemical elementA chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...
with symbol
Sc and
atomic numberIn chemistry and physics, the atomic number is the number of protons found in the nucleus of an atom and therefore identical to the charge number of the nucleus. It is conventionally represented by the symbol Z. The atomic number uniquely identifies a chemical element...
21. A silvery-white metallic
transition metalThe term transition metal has two possible meanings:*The IUPAC definition states that a transition metal is "an element whose atom has an incomplete d sub-shell, or which can give rise to cations with an incomplete d sub-shell." Group 12 elements are not transition metals in this definition.*Some...
, it has historically been sometimes classified as a
rare earth elementAs defined by IUPAC, rare earth elements or rare earth metals are a set of seventeen chemical elements in the periodic table, specifically the fifteen lanthanides plus scandium and yttrium...
, together with
yttriumYttrium is a chemical element with symbol Y and atomic number 39. It is a silvery-metallic transition metal chemically similar to the lanthanides and it has often been classified as a "rare earth element". Yttrium is almost always found combined with the lanthanides in rare earth minerals and is...
and the lanthanoids. It was discovered in 1879 by spectral analysis, of the minerals
euxeniteEuxenite or euxenite- is a brownish black mineral with a metallic luster.-Chemistry:It contains calcium, niobium, tantalum, cerium, titanium, yttrium, and typically uranium and thorium, with some other metals. The chemical formula is: 2O6...
and
gadoliniteGadolinite, sometimes also known as Ytterbite, is a silicate mineral which consists principally of the silicates of cerium, lanthanum, neodymium, yttrium, beryllium, and iron with the formula 2FeBe2Si2O10...
from
ScandinaviaScandinavia is a cultural, historical and ethno-linguistic region in northern Europe that includes the three kingdoms of Denmark, Norway and Sweden, characterized by their common ethno-cultural heritage and language. Modern Norway and Sweden proper are situated on the Scandinavian Peninsula,...
.
Scandium is present in most of the deposits of rare earth and
uraniumUranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...
compounds, but it is extracted from these ores in only a few mines worldwide. Because of the low availability and the difficulties in the preparation of metallic scandium, which was first done in 1937, it took until the 1970s before applications for scandium were developed. The positive effects of scandium on
aluminiumAluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
alloys were discovered in the 1970s, and its use in such alloys remains its only major application.
The properties of scandium compounds are intermediate between those of
aluminiumAluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
and yttrium. A
diagonal relationshipA diagonal relationship is said to exist between certain pairs of diagonally adjacent elements in the second and third periods of the periodic table...
exists between the behavior of
magnesiumMagnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
and scandium, just as there is between
berylliumBeryllium is the chemical element with the symbol Be and atomic number 4. It is a divalent element which occurs naturally only in combination with other elements in minerals. Notable gemstones which contain beryllium include beryl and chrysoberyl...
and aluminium. In the chemical compounds of the elements shown as group 3, above, the predominant oxidation state is +3.
Chemical characteristics of the element
Scandium metal is 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 acidNitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...
(HNO
3) and
hydrofluoric acidHydrofluoric acid is a solution of hydrogen fluoride in water. It is a valued source of fluorine and is the precursor to numerous pharmaceuticals such as fluoxetine and diverse materials such as PTFE ....
(HF), possibly due to the formation of an impermeable
passive layerPassivation is the process of making a material "passive", and thus less reactive with surrounding air, water, or other gases or liquids. The goal is to inhibit corrosion, whether for structural or cosmetic reasons. Passivation of metals is usually achieved by the deposition of a layer of oxide...
.
Isotopes
Scandium exists naturally exclusively as the
isotopeIsotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
45Sc, which has a nuclear spin of 7/2. Thirteen radioisotopes have been characterized with the most stable being
46Sc with a
half-lifeHalf-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
of 83.8 days,
47Sc with a half-life of 3.35 days, and
48Sc with a half-life of 43.7 hours. All of the remaining radioactive isotopes have half-lives that are less than 4 hours, and the majority of these have half-lives that are less than 2 minutes. This element also has five meta states with the most stable being
44mSc (t
½ = 58.6 h).
The isotopes of scandium range from
36Sc to
60Sc. The primary decay mode at masses lower than the only stable isotope,
45Sc, is
electron captureElectron capture is a process in which a proton-rich nuclide absorbs an inner atomic electron and simultaneously emits a neutrino...
, and the primary mode at masses above it is beta emission. The primary
decay productIn nuclear physics, a decay product is the remaining nuclide left over from radioactive decay. Radioactive decay often involves a sequence of steps...
s at atomic weights below
45Sc are
calciumCalcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
isotopes and the primary products from higher atomic weights are
titaniumTitanium is a chemical element with the symbol Ti and atomic number 22. It has a low density and is a strong, lustrous, corrosion-resistant transition metal with a silver color....
isotopes.
Occurrence
In terms of
earth's crustThe table shows the abundance of elements in Earth's crust. Numbers show percentage or parts per million in mass; 10,000 ppm = 1%.Note that numbers are estimates, and they will vary depending on source and method of estimation. Order of magnitude of data can roughly be relied upon.The table shows...
, scandium is not particularly 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 in the crust, but it is the 23rd most common element in the sun). However, scandium is distributed sparsely and occurs in trace amounts in many
mineralA mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...
s. Rare minerals from Scandinavia and
MadagascarThe Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
such as
thortveititeThortveitite is a mineral consisting of scandium yttrium silicate 2Si2O7. It is the primary source of scandium. Occurrence is in granitic pegmatites. It was named after Olaus Thortveit, Norwegian engineer. It is greyish-green, black or grey in color....
,
euxeniteEuxenite or euxenite- is a brownish black mineral with a metallic luster.-Chemistry:It contains calcium, niobium, tantalum, cerium, titanium, yttrium, and typically uranium and thorium, with some other metals. The chemical formula is: 2O6...
, and
gadoliniteGadolinite, sometimes also known as Ytterbite, is a silicate mineral which consists principally of the silicates of cerium, lanthanum, neodymium, yttrium, beryllium, and iron with the formula 2FeBe2Si2O10...
are the only known concentrated sources of this element. Thortveitite can contain up to 45% of scandium in the form of
scandium(III) oxideScandium oxide, Sc2O3, scandia is a high melting white solid used in high-temperature systems , electronic ceramics, and glass composition .-Physical and chemical properties:...
.
The stable form of scandium is created in
supernovaA supernova is a stellar explosion that is more energetic than a nova. It is pronounced with the plural supernovae or supernovas. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months...
s via the
r-processThe r-process is a nucleosynthesis process, likely occurring in core-collapse supernovae responsible for the creation of approximately half of the neutron-rich atomic nuclei that are heavier than iron. The process entails a succession of rapid neutron captures on seed nuclei, typically Ni-56,...
.
Production
World production of scandium is in the order of 2 tonnes per year in the form of scandium oxide. The primary production is 400 kg while the rest is from stockpiles of Russia generated during the
Cold WarThe Cold War was the continuing state from roughly 1946 to 1991 of political conflict, military tension, proxy wars, and economic competition between the Communist World—primarily the Soviet Union and its satellite states and allies—and the powers of the Western world, primarily the United States...
. In 2003, only three mines produced scandium: the uranium and iron mines in
Zhovti VodyZhovti Vody is a city in south-central Ukraine's Dnipropetrovsk Oblast . The city is designated as a separate raion within the oblast, and is located on the Yellow River approximately west of the oblast's administrative center, Dnipropetrovsk.Center for the extraction and processing of uranium...
in
UkraineUkraine is a country in Eastern Europe. It has an area of 603,628 km², making it the second largest contiguous country on the European continent, after Russia...
, the rare earth mines in
Bayan OboBayan Obo Mining District, , or Baiyun-Obo or Baiyun'ebo, is a mining town in the west of Inner Mongolia, People's Republic of China. It is under the administration of Baotou City, more than to the south....
,
ChinaChinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
and the apatite mines in the
Kola peninsulaThe Kola Peninsula is a peninsula in the far northwest of Russia. Constituting the bulk of the territory of Murmansk Oblast, it lies almost completely to the north of the Arctic Circle and is washed by the Barents Sea in the north and the White Sea in the east and southeast...
,
RussiaRussia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
. In each case, scandium is a byproduct from the extraction of other elements and is sold as scandium oxide.
The production of metallic scandium is in the order of 10 kg per year. The oxide is converted to
scandium fluorideScandium fluoride, ScF3, is an ionic compound. It is slightly soluble in water but dissolves in the presence of excess fluoride to form ScF63−. ScF3 can be produced by reacting scandium and fluorine...
and
reducedRedox reactions describe all chemical reactions in which atoms have their oxidation state changed....
with metallic
calciumCalcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
.
MadagascarThe Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
and
IvelandIveland is a village and municipality in Aust-Agder county, Norway. It is part of the traditional region of Sørlandet. The administrative center is the village of Birketveit.-General information:...
-
EvjeEvje is a village and former municipality in Aust-Agder county, Norway. The village of Evje is the administrative center of the current municipality of Evje og Hornnes in the Setesdal valley region...
region in
NorwayNorway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
have the only deposits of minerals with high scandium content,
thortveititeThortveitite is a mineral consisting of scandium yttrium silicate 2Si2O7. It is the primary source of scandium. Occurrence is in granitic pegmatites. It was named after Olaus Thortveit, Norwegian engineer. It is greyish-green, black or grey in color....
(Sc,Y)
2(Si
2O
7) and
kolbeckite ScPO
4·2H
2O, but these are not being exploited.
The absence of reliable, secure, stable and long term production has limited 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. Scandium-stabilized zirconia enjoys a growing market demand for use as a high efficiency electrolyte in solid oxide fuel cells.
Compounds
The chemistry is almost completely dominated by the trivalent ion, Sc
3+. The radii of M
3+ ions in the table below indicate that in terms of chemical properties, scandium ions are more similar to those of yttrium than to those of aluminium. In part for this similarity, scandium is often classified as a lanthanide-like element.
Ionic radii (pm)
AlAluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
|
Sc |
YYttrium is a chemical element with symbol Y and atomic number 39. It is a silvery-metallic transition metal chemically similar to the lanthanides and it has often been classified as a "rare earth element". Yttrium is almost always found combined with the lanthanides in rare earth minerals and is...
|
LaLanthanum is a chemical element with the symbol La and atomic number 57.Lanthanum is a silvery white metallic element that belongs to group 3 of the periodic table and is the first element of the lanthanide series. It is found in some rare-earth minerals, usually in combination with cerium and...
|
Lu |
| 53.5 |
74.5 |
90.0 |
103.2 |
86.1 |
Oxides and hydroxides
The oxide Sc
2O
3 and the hydroxide Sc(OH)
3 are amphoteric:
- Sc(OH)3 + 3 OH− → Sc
- Sc(OH)3 + 3 H+ + 3 H2O → [Sc(H2O)6]3+
The α- and γ- forms of scandium oxide hydroxide (ScO(OH)), are isostructural with their
aluminium oxide hydroxideAluminium hydroxide oxide or aluminium oxyhydroxide, AlO is found as one of two well defined crystalline phases, which are also known as the minerals boehmite and diaspore...
counterparts. Solutions of Sc
3+ in water are acidic because of
hydrolysisHydrolysis is a chemical reaction during which molecules of water are split into hydrogen cations and hydroxide anions in the process of a chemical mechanism. It is the type of reaction that is used to break down certain polymers, especially those made by condensation polymerization...
.
Halides and pseudohalides
The halides ScX
3 (X =
ClScandium chloride is the inorganic compound with the formula ScCl3. It is a white, high-melting ionic compound, which is deliquescent and highly water soluble. Scandium chloride is mainly of interest in the research laboratory...
, Br, I) are very soluble in water, but ScF
3 is insoluble. In all four halides the scandium is 6-coordinated. The halides are Lewis acids; for example, ScF
3 dissolves a solution containing excess fluoride to form [ScF
6]
3−. The coordination number 6 is typical of Sc(III). In the larger Y
3+ and La
3+ ions,
coordination numberIn chemistry and crystallography, the coordination number of a central atom in a molecule or crystal is the number of its nearest neighbours. This number is determined somewhat differently for molecules and for crystals....
s of 8 and 9 are common.
Scandium(III) triflateScandium trifluoromethanesulfonate, commonly called scandium triflate, is a chemical compound with formula Sc3, a salt consisting of scandium cations Sc3+ and triflate SO3CF3− anions....
is sometimes used as a
Lewis acid]The term Lewis acid refers to a definition of acid published by Gilbert N. Lewis in 1923, specifically: An acid substance is one which can employ a lone pair from another molecule in completing the stable group of one of its own atoms. Thus, H+ is a Lewis acid, since it can accept a lone pair,...
catalyst in
organic chemistryOrganic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, composition, reactions, and preparation of carbon-based compounds, hydrocarbons, and their derivatives...
.
Organic derivatives
Scandium forms a series of organometallic compounds with
cyclopentadienylA cyclopentadienyl complex is a metal complex with one or more cyclopentadienyl groups . Based on the type of bonding between the metals and the cyclopentadienyl]] moieties, cyclopentadienyl complexes are classified into the following three categories: a) π-complexes, b) σ-complexes, and c) ionic...
ligands (Cp), similar to the behavior of the lanthanide. One example is the chlorine-bridged dimer, [ScCp
2Cl]
2 and related derivatives of pentamethylcyclopentadienyl ligands.
Uncommon oxidation states
Compounds that feature scandium in the oxidation state other than +3 are rare but well characterized. The blue-black compound CsScCl
3 is one of the simplest. This material adopts a sheet-like structure that exhibits extensive bonding between the scandium(II) centers.
Scandium hydrideScandium hydride is a chemical compound with formula ScH3. It can form by direct reaction of scandium and hydrogen at elevated temperatures. The exact composition varies....
is not well understood, although it appears not to be a
saline hydrideIn chemistry, a hydride is the anion of hydrogen, H−, or, more commonly, a compound in which one or more hydrogen centres have nucleophilic, reducing, or basic properties. In compounds that are regarded as hydrides, hydrogen is bonded to a more electropositive element or group...
of Sc(II). As is observed for most elements, a diatomic scandium hydride has been observed spectroscopically at high temperatures in the gas phase. Scandium borides and carbides are
non-stoichiometricNon-stoichiometric compounds are chemical compounds with an elemental composition that cannot be represented by a ratio of well-defined natural numbers, and therefore violate the law of definite proportions. Often, they are solids that contain crystallographic point defects, such as interstitial...
, as is typical for neighboring elements.
History
Dmitri MendeleevDmitri Ivanovich Mendeleev , was a Russian chemist and inventor. He is credited as being the creator of the first version of the periodic table of elements...
, creator of the
periodic tableThe periodic table of the chemical elements is a tabular display of the 118 known chemical elements organized by selected properties of their atomic structures. Elements are presented by increasing atomic number, the number of protons in an atom's atomic nucleus...
, predicted the existence of an element
ekaboron, with an
atomic massThe atomic mass is the mass of a specific isotope, most often expressed in unified atomic mass units. The atomic mass is the total mass of protons, neutrons and electrons in a single atom....
between 40 and 48 in 1869.
Lars Fredrik NilsonLars Fredrik Nilson was a Swedish chemist who discovered scandium in 1879.Nilson was born in Skönberga parish in Östergötland, Sweden. His father, Nikolaus, was a farmer. The family moved to Gotland when Lars Fredrik was young. After graduating from school, Lars Fredrik enrolled at Uppsala...
and his team detected this element in the minerals
euxeniteEuxenite or euxenite- is a brownish black mineral with a metallic luster.-Chemistry:It contains calcium, niobium, tantalum, cerium, titanium, yttrium, and typically uranium and thorium, with some other metals. The chemical formula is: 2O6...
and
gadoliniteGadolinite, sometimes also known as Ytterbite, is a silicate mineral which consists principally of the silicates of cerium, lanthanum, neodymium, yttrium, beryllium, and iron with the formula 2FeBe2Si2O10...
. Nilson prepared 2 grams of scandium oxide of high purity. He named the element scandium, from the
LatinLatin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
Scandia meaning "Scandinavia". Nilson was apparently unaware of Mendeleev's prediction, but
Per Teodor ClevePer Teodor Cleve was a Swedish chemist and geologist.After graduating from the Stockholm Gymnasium in 1858, Cleve matriculated at Uppsala University in May 1858, where he received his PhD in 1863...
recognized the correspondence and notified Mendeleev.
Metallic scandium was produced for the first time in 1937 by
electrolysisIn chemistry and manufacturing, electrolysis is a method of using a direct electric current to drive an otherwise non-spontaneous chemical reaction...
of a eutectic mixture, at 700–800 °
CCelsius is a scale and unit of measurement for temperature. It is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death...
, of
potassiumPotassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...
,
lithiumLithium is a soft, silver-white metal that belongs to the alkali metal group of chemical elements. It is represented by the symbol Li, and it has the atomic number 3. Under standard conditions it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly...
, and scandium chlorides. The first pound of 99% pure scandium metal was produced in 1960. The use for aluminium alloys began in 1971, following a US patent. Aluminium-scandium alloys were also developed in the USSR.
Applications
The addition of scandium to aluminium limits the excessive grain growth that occurs in the heat-affected zone of welded aluminium components. This has two beneficial effects: the precipitated Al
3Sc forms smaller crystals than are formed in other
aluminium alloyAluminium alloys are alloys in which aluminium is the predominant metal. The typical alloying elements are copper, magnesium, manganese, silicon and zinc. There are two principal classifications, namely casting alloys and wrought alloys, both of which are further subdivided into the categories...
s and the volume of precipitate-free zones that normally exist at the grain boundaries of age-hardening aluminium alloys is reduced. Both of these effects increase the usefulness of the alloy. However,
titanium alloyTitanium alloys are metallic materials which contain a mixture of titanium and other chemical elements. Such alloys have very high tensile strength and toughness , light weight, extraordinary corrosion resistance, and ability to withstand extreme temperatures...
s, which are similar in lightness and strength, are cheaper and much more widely used.
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 the Russian military aircraft, specifically the
MiG-21The Mikoyan-Gurevich MiG-21 is a supersonic jet fighter aircraft, designed by the Mikoyan-Gurevich Design Bureau in the Soviet Union. It was popularly nicknamed "balalaika", from the aircraft's planform-view resemblance to the Russian stringed musical instrument or ołówek by Polish pilots due to...
and MiG-29.
Some items of sports equipment, which rely on high performance materials, have been made with scandium-aluminium alloys, including
baseball batA baseball bat is a smooth wooden or metal club used in the game of baseball to hit the ball after the ball is thrown by the pitcher. It is no more than 2.75 inches in diameter at the thickest part and no more than 42 inches in length. It typically weighs no more than 33 ounces , but it...
s, and
bicycleA bicycle, also known as a bike, pushbike or cycle, is a human-powered, pedal-driven, single-track vehicle, having two wheels attached to a frame, one behind the other. A person who rides a bicycle is called a cyclist, or bicyclist....
frames and components. Lacrosse sticks are also made with scandium-titanium alloys to take advantage of the strength of titanium. The American firearm manufacturing company
Smith & WessonSmith & Wesson is the largest manufacturer of handguns in the United States. The corporate headquarters is in Springfield, Massachusetts. Founded in 1852, Smith & Wesson's pistols and revolvers have become standard issue to police and armed forces throughout the world...
produces revolvers with frames composed of scandium alloy and cylinders of titanium or carbon steel.
Approximately 20 kg (as Sc
2OOxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
3) of scandium is used annually in the
United StatesThe United States of America is a federal constitutional republic comprising fifty states and a federal district...
to make high-intensity discharge lamps. Scandium iodide, along with
sodium iodideSodium iodide is a white, crystalline salt with chemical formula NaI used in radiation detection, treatment of iodine deficiency, and as a reactant in the Finkelstein reaction.-Uses:Sodium iodide is commonly used to treat and prevent iodine deficiency....
, when added to a modified form of
mercury-vapor lampA mercury-vapor lamp is a gas discharge lamp that uses an electric arc through vaporized mercury to produce light. The arc discharge is generally confined to a small fused quartz arc tube mounted within a larger borosilicate glass bulb...
, produces a form of
metal halide lampMetal-halide lamps, a member of the high-intensity discharge family of lamps, produce high light output for their size, making them a compact, powerful, and efficient light source. By adding rare earth metal salts to the mercury vapor lamp, improved luminous efficacy and light color is obtained...
. This lamp is a white light source with high color rendering index that sufficiently resembles sunlight to allow good color-reproduction with
TVTelevision is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...
cameras. About 80 kg of scandium is used in metal halide lamps/light bulbs globally per year. The first scandium-based metal halide lamps were patented by
General ElectricGeneral Electric Company , or GE, is an American multinational conglomerate corporation incorporated in Schenectady, New York and headquartered in Fairfield, Connecticut, United States...
and initially made in North America, although they are now produced in all major industrialized countries. The radioactive isotope
46Sc is used in
oil refineriesAn oil refinery or petroleum refinery is an industrial process plant where crude oil is processed and refined into more useful petroleum products, such as gasoline, diesel fuel, asphalt base, heating oil, kerosene, and liquefied petroleum gas...
as a tracing agent. Scandium triflate is a catalytic
Lewis acid]The term Lewis acid refers to a definition of acid published by Gilbert N. Lewis in 1923, specifically: An acid substance is one which can employ a lone pair from another molecule in completing the stable group of one of its own atoms. Thus, H+ is a Lewis acid, since it can accept a lone pair,...
used in
organic chemistryOrganic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, composition, reactions, and preparation of carbon-based compounds, hydrocarbons, and their derivatives...
.
Health and safety
Elemental scandium is considered non-toxic and little animal testing of scandium compounds has been done. The median lethal dose (LD
50) levels for scandium(III) chloride for rats have been determined as 4 mg/kg for
intraperitonealIntraperitoneal injection or IP injection is the injection of a substance into the peritoneum . IP injection is more often applied to animals than humans...
and 755 mg/kg for oral administration. In the light of these results compounds of scandium should be handled as compounds of moderate toxicity.
See also
- Rare earth element
As defined by IUPAC, rare earth elements or rare earth metals are a set of seventeen chemical elements in the periodic table, specifically the fifteen lanthanides plus scandium and yttrium...
Further reading
- Eric Scerri, The Periodic System, Its Story and Its Significance, Oxford University Press, New York, 2007.
External links