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. The term is also used to refer to a pure chemical substance composed of atoms with the same number of protons.Common examples of 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:*In the past it referred to any element in the d-block of the periodic table, which includes groups 3 to 12 on the periodic table...
, it has historically been sometimes classified as a
rare earth elementAs defined by IUPAC, rare earth elements or rare earth metals are a collection of seventeen chemical elements in the periodic table, namely scandium, yttrium, and the fifteen lanthanoids...
, 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 lanthanoids and has historically been classified as a rare earth element. Yttrium is almost always found combined with the lanthanoids in rare earth minerals and is...
and the
lanthanideAccording to the IUPAC terminology, the lanthanoid series comprises the fifteen elements with atomic numbers 57 through 71, from lanthanum to lutetium. All lanthanoids are f-block elements, corresponding to the filling of the 4f electron shell, except for lutetium which is a d-block lanthanoid...
s. In 1879,
Lars Fredrik NilsonLars Fredrik Nilson was a Swedish chemist who discovered scandium in 1879.- Life and work :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...
and his team, found a new element with spectral analysis, in the minerals
euxeniteEuxenite or euxenite- is a brownish black mineral with a metallic luster. It contains calcium, niobium, tantalum, cerium, titanium, yttrium, and typically uranium and thorium, with some other metals. The chemical formula is: 2O6. It occurs in granite pegmatites and detrital...
and
gadoliniteGadolinite is a mineral of a nearly black color and vitreous luster, and consisting principally of the silicates of cerium, lanthanum, neodymium, yttrium, beryllium, and iron with formula: 2FeBe2Si2O10...
from
ScandinaviaScandinavia is a geographical region in northern Europe that includes, and is named after, the Scanian Province. It consists of the kingdoms of Norway, Sweden, and Denmark...
.
Scandium is present in most of the rare earth element and
uraniumUranium is a silvery-white metallic chemical element in the actinide series of the periodic table that has the symbol U and atomic number 92. Besides its 92 protons, a uranium nucleus can have between 141 and 146 neutrons. The most common uranium isotopes are U-238 and U-235 . A uranium atom has...
deposits, but it is extracted from these ores in only a few mines worldwide. Due to 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 and ductile member of the boron group of chemical elements. It has the symbol Al; 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 the only major application of scandium.
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...
predicted the existence of an element that he called
ekaboron, with an
atomic massThe atomic mass is the mass of an atom, most often expressed in unified atomic mass units. The atomic mass may be considered to be the total mass of protons, neutrons and electrons in a single atom...
between 40 and 48 in 1869. Ten years later
Lars Fredrik NilsonLars Fredrik Nilson was a Swedish chemist who discovered scandium in 1879.- Life and work :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...
found a new element in the minerals
euxeniteEuxenite or euxenite- is a brownish black mineral with a metallic luster. It contains calcium, niobium, tantalum, cerium, titanium, yttrium, and typically uranium and thorium, with some other metals. The chemical formula is: 2O6. It occurs in granite pegmatites and detrital...
and
gadoliniteGadolinite is a mineral of a nearly black color and vitreous luster, and consisting principally of the silicates of cerium, lanthanum, neodymium, yttrium, beryllium, and iron with formula: 2FeBe2Si2O10...
from Scandinavia. He was able to prepare 2 g of scandium oxide of high purity. He named it scandium, from the
LatinLatin is an Italic language originally spoken in Latium and Ancient Rome. Through the Roman conquest, Latin spread throughout the Mediterranean and a large part of Europe...
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 an electric current to drive an otherwise non-spontaneous chemical reaction. Electrolysis is commercially highly important as a stage in the separation of elements from naturally-occurring sources such as ores using an electrolytic...
of a eutectic mixture, at 700–800 °
CCelsius is a temperature scale that 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 , atomic number 19, and atomic mass 39.0983. Potassium was first isolated from potash...
,
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 three. 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.
Position in the periodic table
Groups 1 to 3 of the periodic table could be written as follows:
| 1 | 2 | 3 |
|---|
| H |
|
|
| Li |
Be |
B |
| Na |
Mg |
Al |
| K |
Ca |
Sc |
| Rb |
Sr |
Y |
| Cs |
Ba |
La |
| Fr |
Ra |
Ac |
This grouping is consistent with Mendeleev's prediction for scandium as "eka-boron". It shows that the properties of Sc will be intermediate between the properties of Al and Y, in the same way that the properties of Ca are intermediate between those of Mg and Sr. It also shows that there will be 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...
between Mg and Sc, just as there is between Be and Al.
However, in the standard periodic table boron and aluminium are placed in group 13, where the relationships above are less obvious. As to the rest of group 3, there has been controversy as to whether
yttriumYttrium is a chemical element with symbol Y and atomic number 39. It is a silvery-metallic transition metal chemically similar to the lanthanoids and has historically been classified as a rare earth element. Yttrium is almost always found combined with the lanthanoids in rare earth minerals and is...
is in the same group as
lanthanumLanthanum 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 a lanthanoid. It is found in some rare-earth minerals, usually in combination with cerium and other rare earth elements...
or as
lutetiumLutetium is a chemical element with the symbol Lu and atomic number 71. It is in the d-block of the periodic table, not the f-block, but the IUPAC classifies it as a lanthanide. It is one of the elements that traditionally was included in the classification, "rare earths"...
. In the chemical compounds of the elements shown as group 3, above, the predominant oxidation state is +3. The ions M
3+ will all have the electronic configuration of a noble gas, so it is reasonable that they should be in the same group of the periodic table. Most modern text-books place Sc, Y, La and Ac in the same periodic group.
Occurrence
Scandium does not have a particularly low
abundanceThe abundance of a chemical element measures how relatively common the element is, or how much of the element there is by comparison to all other elements. Abundance may be variously measured by the mass-fraction , or mole-fraction , or by volume fraction...
in the
earth's crustThis table shows the abundance of elements in Earth's crust. Numbers show percentage in mass.Note that numbers are estimates, and they will vary depending on source and method of estimation...
. Estimates vary from 18 to 25 ppm, which is comparable to the abundance of cobalt (20–30 ppm). However, scandium is distributed sparsely and occurs in trace amounts in many
mineralA mineral is a naturally occurring solid formed through geological processes that has a characteristic chemical composition, a highly ordered atomic structure, and specific physical properties. A rock, by comparison, is an aggregate of minerals and/or mineraloids, and need not have a specific...
s. Rare minerals from Scandinavia and
MadagascarMadagascar, or Republic of Madagascar , is an island nation in the Indian Ocean off the southeastern coast of Africa. The main island, also called Madagascar, is the fourth-largest island in the world, and is home to 5% of the world's plant and animal species, of which more than 80% are endemic to...
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...
,
euxeniteEuxenite or euxenite- is a brownish black mineral with a metallic luster. It contains calcium, niobium, tantalum, cerium, titanium, yttrium, and typically uranium and thorium, with some other metals. The chemical formula is: 2O6. It occurs in granite pegmatites and detrital...
, and
gadoliniteGadolinite is a mineral of a nearly black color and vitreous luster, and consisting principally of the silicates of cerium, lanthanum, neodymium, yttrium, beryllium, and iron with formula: 2FeBe2Si2O10...
are the only known concentrated sources of this element. Thortveitite can contain up to 45%, as scandium(III) oxide.
Scandium is more common in the sun and certain
starA star is a massive, luminous ball of plasma that is held together by gravity. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth. Other stars are visible in the night sky, when they are not outshone by the Sun...
s than on
EarthEarth is the third planet from the Sun. It is the fifth largest of the eight planets in the solar system, and the largest of the terrestrial planets in the Solar System in terms of diameter, mass and density...
. Scandium is only the 50th most common element on earth (35th most abundant in the Earth's
crustIn geology, a crust is the outermost solid shell of a rocky planet or moon, which is chemically distinct from the underlying mantle. The crusts of Earth, our Moon, Mercury, Venus, Mars, Io, and other planetary bodies have been generated largely by igneous processes, and these crusts are richer in...
), but it is the 23rd most common element in the sun.
Production
World production of scandium is in the order of 2,000 kg per year as scandium oxide. The primary production is 400 kg while the rest is from stockpiles of Russia created during the
Cold WarThe Cold War was the continuing state of political conflict, military tension, and economic competition existing after World War II , primarily between the USSR and its satellite states, and the powers of the Western world, including 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 130km west of the oblast's administrative center, Dnipropetrovsk.The historic Battle of Zhovti Vody was fought...
in
UkraineUkraine is a country in Eastern Europe. It is bordered by Russia to the east; Belarus to the north; Poland, Slovakia, and Hungary to the west; Romania and Moldova to the southwest; and the Black Sea and Sea of Azov to the south. The city of Kiev is both the capital and the largest city of...
, the rare earth mines in
Bayan OboBayan Obo is a mining town in the autonomous region Inner Mongolia, northern China.The mines north of the town are the largest deposits of rare earth metals yet found....
,
ChinaChina is a cultural region, an ancient civilization, and, depending on perspective, a national or multinational entity extending over a large area in East Asia....
and the apatite mines in the
Kola peninsulaThe Kola Peninsula is a peninsula in the far north of Russia, part of the Murmansk Oblast. It borders upon the Barents Sea on the North and the White Sea on the East and South...
,
RussiaRussia , officially known as both Russia and the Russian Federation , is a country in northern Eurasia . It is a 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−.
...
and
reducedRedox describes all chemical reactions in which atoms have their oxidation number 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 grey alkaline earth metal, and is the fifth most abundant element by mass in the Earth's crust...
.
MadagascarMadagascar, or Republic of Madagascar , is an island nation in the Indian Ocean off the southeastern coast of Africa. The main island, also called Madagascar, is the fourth-largest island in the world, and is home to 5% of the world's plant and animal species, of which more than 80% are endemic to...
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 country in Northern Europe occupying the western portion of the Scandinavian Peninsula, as well as Jan Mayen and the Arctic archipelago of Svalbard under the Spitsbergen Treaty...
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...
(Y,Sc)
2(Si
2O
7) and
kolbeckiteKolbeckite is a scandium phosphate mineral with formula: ScPO4·2H2O. It was discovered originally at Schmiedeberg, Saxony, Germany in 1926 and is named after Friedrich LW Kolbeck, a German mineralogist. Kolbeckite is usually found as small clusters of crystals...
ScPO
4·2H
2O, but these are not being exploited. Other scandium sources include the nickel and cobalt mines at Syerston and Lake Innes,
New South WalesNew South Wales is Australia's most populous state, located in the south-east of the country, north of Victoria, south of Queensland and east of South Australia...
,
AustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the continental mainland , the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans...
,
ironIron is a metallic chemical element with the symbol Fe and atomic number 26. Iron is a group 8 and period 4 element and is therefore classified as a transition metal. Iron and iron alloys are by far the most common metals and the most common ferromagnetic materials in everyday use...
,
tinTin is a chemical element with the symbol Sn and atomic number 50. It is a main group metal in group 14 of the periodic table. Tin shows chemical similarity to both neighboring group 14 elements, germanium and lead, like the two possible oxidation states +2 and +4...
, and
tungstenTungsten , also known as wolfram , is a chemical element with the chemical symbol W and atomic number 74.A steel-gray metal, tungsten is found in several ores, including wolframite and scheelite...
deposits in China and
uraniumUranium is a silvery-white metallic chemical element in the actinide series of the periodic table that has the symbol U and atomic number 92. Besides its 92 protons, a uranium nucleus can have between 141 and 146 neutrons. The most common uranium isotopes are U-238 and U-235 . A uranium atom has...
deposits in
RussiaRussia , officially known as both Russia and the Russian Federation , is a country in northern Eurasia . It is a semi-presidential republic, comprising 83 federal subjects...
and
KazakhstanKazakhstan , officially the Republic of Kazakhstan, is a country situated in Eurasia that is ranked as the ninth largest country in the world. It is also the world's largest landlocked country. Its territory of 2,727,300 km² is greater than Western Europe...
. As of 2003, scandium was not being extracted from the
tailingsTailings are the materials left over after the process of separating the valuable fraction from the worthless fraction of an ore....
at any of these mines, but some scandium extraction may be started if there is sufficient demand. There is currently no primary production of scandium in the Americas, Europe, or Australia.
Isotopes
Naturally occurring scandium is composed of one stable
isotopeIsotopes are different types of atoms of the same chemical element, each having a different number of neutrons. Correspondingly, isotopes differ in mass number but not in atomic number. The difference in the number of nucleons comes from a difference how many neutrons are in the atomic nucleus...
45Sc with a nuclear spin of 7/2. 13 radioisotopes have been characterized with the most stable being
46Sc with a
half-lifeHalf-life is the period of time, for a substance undergoing decay, to decrease by half. The name originally was used to describe a characteristic of unstable atoms , but may apply to any quantity which follows a set-rate decay....
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 5 meta states with the most stable being
44mSc (t
½ 58.6 h).
The isotopes of scandium range in
atomic weightAtomic weight is a dimensionless physical quantity, the ratio of the average mass of atoms of an element to 1/12 of the mass of an atom of carbon-12...
from 40
uThe unified atomic mass unit or atomic mass unit , or dalton or, sometimes, universal mass unit , is a unit of mass used to express atomic and molecular masses...
(
40Sc) to 54 u (
54Sc). The primary decay mode at masses lower than the only stable isotope,
45Sc, is
electron captureElectron capture is a decay mode for isotopes that will occur when there are too many protons in the nucleus of an atom and insufficient energy to emit a positron; however, it continues to be a viable decay mode for radioactive isotopes that can decay by positron emission...
, and the primary mode at masses above it is beta emission. The primary
decay productIn nuclear physics, a decay product is a nuclide produced by 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 grey 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. Sometimes called the “space age metal”, it has a low density and is a strong, lustrous, corrosion-resistant transition metal with a silver color.Titanium can be alloyed with iron, aluminium, vanadium, molybdenum, among other...
isotopes.
Compounds
Scandium metal is hard and has a silvery appearance. It develops a slightly yellowish or pinkish cast when exposed to air. It is not resistant 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 stronger yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as...
(
HHydrogen is the chemical element with atomic number 1. It is represented by the symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly flammable diatomic gas with the molecular formula H
2...
NNitrogen is a chemical element that has the symbol N and atomic number 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78% by volume of Earth's atmosphere.Many industrially important...
OOxygen Oxygen Oxygen (acid, literally "sharp", from the taste of acids) and -γενής (-genēs) (producer, literally begetter) is the element with atomic number 8 and represented by the symbol O...
3) and
hydrofluoric acidHydrofluoric acid is a solution of hydrogen fluoride in water. While it is extremely corrosive and difficult to handle, it is technically a weak acid...
,
HHydrogen is the chemical element with atomic number 1. It is represented by the symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly flammable diatomic gas with the molecular formula H
2...
FFluorine is the chemical element with atomic number 9, represented by the symbol F. Fluorine forms a single bond with itself in elemental form, resulting in the diatomic F
2 molecule. F
2 is a supremely reactive, poisonous, pale, yellowish brown gas. Elemental fluorine is the...
, presumably due to the formation of an impermeable
passive layerPassivation is the process of making a material "passive" in relation to another material prior to using the materials together. For example, prior to storing hydrogen peroxide in an aluminium container, the container can be passivated by rinsing it with a dilute solution of nitric acid and...
on the surface of the metal. In the compounds ScB and ScC, boron and carbon are incorporated
non-stoichiometricallyNon-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...
into the lattice of the scandium.
The radii of M
3+ ions in the following table
Ionic radii (pm)
AlAluminium or aluminum is a silvery white and ductile member of the boron group of chemical elements. It has the symbol Al; 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 lanthanoids and has historically been classified as a rare earth element. Yttrium is almost always found combined with the lanthanoids 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 a lanthanoid. It is found in some rare-earth minerals, usually in combination with cerium and other rare earth elements...
|
LuLutetium is a chemical element with the symbol Lu and atomic number 71. It is in the d-block of the periodic table, not the f-block, but the IUPAC classifies it as a lanthanide. It is one of the elements that traditionally was included in the classification, "rare earths"...
|
| 53.5 |
74.5 |
90.0 |
103.2 |
86.1 |
indicate why the chemistry of scandium is more closely related to that of
yttriumYttrium is a chemical element with symbol Y and atomic number 39. It is a silvery-metallic transition metal chemically similar to the lanthanoids and has historically been classified as a rare earth element. Yttrium is almost always found combined with the lanthanoids in rare earth minerals and is...
than that of
aluminiumAluminium or aluminum is a silvery white and ductile member of the boron group of chemical elements. It has the symbol Al; its atomic number is 13. It is not soluble in water under normal circumstances....
and explains why scandium has been classified as a lanthanide-like element. The oxide Sc
2O
3 is weakly acidic and the hydroxide Sc(OH)
3 is amphoteric:
- Sc3+ (aq) ← H+ + Sc(OH)3 + OH− → Sc
The α- and γ - forms of scandium oxide hydroxide (ScO(OH)), are isostructural with their
aluminium oxide hydroxideAluminium hydroxide oxide or aluminium oxyhydroxide 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 one or more water molecules are split into hydrogen and hydroxide ions, which may go on to participate in further reactions. It is the type of reaction that is used to break down certain polymers, especially those made by step-growth polymerization...
.
The halides ScX
3 (X =
ClScandium chloride, ScCl3, is a white ionic compound which is deliquescent and highly water soluble.-Chemical and physical properties:ScCl3 has the BiI3 layered structure, with 6 coordinate scandium ions...
, Br, I) are very soluble in water, but ScF
3 is insoluble. In all four halides the scandium is 6-coordinate. The halides are Lewis acids; for example, ScF
3 dissolves a solution containing excess fluoride to form [ScF
6]
3−. This is a typical example of a complex of Sc(III) in which the coordination number is 6. In the larger Y and La ions 8- and 9- coordination are often found.
There are a few compounds known in which the oxidation state is less than 3. The cluster [Sc
6Cl
12]
3− has a similar structure to that of the Nb
6Cl
12 cluster in which chlorine atoms bridge the 12 edges of an octahedron of metal atoms. Other sub-halides are known. The nature of the hydride ScH
2 is not yet fully understood. It appears not to be a
saline hydrideHydride is the name given to the negative ion of hydrogen, H−. Practically, the term hydride has two distinct but overlapping meanings. In the chemical vernacular the term hydride refers to a hydrogen atom that formally reacts as a hydrogen anion under common conditions as well as...
of Sc(II), but may be a compound of Sc(III) with two hydrides and an electron which is delocalized in a kind of metallic structure. ScH can be observed spectroscopically at high temperatures in the gas phase.
Scandium forms a series of organometallic compounds with
cyclopentadienylA cyclopentadienyl complex is a metal complex with one or more cyclopentadienyl groups...
, based on the Sc(Cp)
2 motif. The chlorine-bridged dimer, [Sc(Cp)
2Cl]
2 is the starting point for the preparation of many compounds by replacement of the chlorine.
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 mixtures of aluminium with other metals , often with copper, zinc, manganese, silicon, or magnesium. They are much lighter and more corrosion resistant than plain carbon steel, but not as corrosion resistant as pure aluminium...
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
alloyAn alloy is a partial or complete solid solution of one or more elements in a metallic matrix. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may be homogeneous in distribution depending on thermal history...
s for minor aerospace industry components. These alloys contain between 0.1% and 0.5% of scandium. They were used in the Russian military aircraft Mig 21 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...
s,
lacrosseLacrosse is a team sport of Native American origin that is played using a small solid rubber ball and a long-handled racquet called a crosse or lacrosse stick. The head of the lacrosse stick is strung with loose netting that is designed to hold the lacrosse ball...
sticks, as well as
bicycleA bicycle, also known as a bike, push bike or cycle, is a pedal-driven, human-powered vehicle with two wheels attached to a frame, one behind the other. A person who rides a bicycle is called a cyclist or a bicyclist....
frames and components. U.S. gunmaker
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.
Approximately 20 kg (as Sc
2OOxygen Oxygen Oxygen (acid, literally "sharp", from the taste of acids) and -γενής (-genēs) (producer, literally begetter) is the element with atomic number 8 and represented by the symbol O...
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 which uses mercury in an excited state 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. Originally created in the late 1960s for industrial use, metal halide lamps are now available in numerous sizes and...
, an artificial light source which produce a very white light with high colour rendering index that sufficiently resembles sunlight to allow good color-reproduction with
TVTelevision is a widely used telecommunication medium for transmitting and receiving moving images, either monochromatic or color, usually accompanied by sound. "Television" may also refer specifically to a television set, television programming or television transmission...
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 Electric 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 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 acidA Lewis acid, A, is a chemical compound that can accept a pair of electrons from a Lewis base, B, that acts as an electron-pair donor, forming an adduct, AB:
A + :B → A—B...
used in
organic chemistryOrganic chemistry is a discipline within chemistry which involves the scientific study of the structure, properties, composition, reactions, and preparation of chemical compounds that contain carbon...
.
Health and safety
The pure metal is not considered to be toxic. 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 and were
intraperitonealIntraperitoneal injection or IP injection is the injection of a substance into the peritoneum . IP injection is more often applied to animals than humans...
4 mg/kg and oral 755 mg/kg. In the light of these results compounds of scandium should be handled as compounds of moderate toxicity.
See also
- Scandium compounds
- Scandium minerals
- Yttrium
Yttrium is a chemical element with symbol Y and atomic number 39. It is a silvery-metallic transition metal chemically similar to the lanthanoids and has historically been classified as a rare earth element. Yttrium is almost always found combined with the lanthanoids in rare earth minerals and is...
- Rare earth element
As defined by IUPAC, rare earth elements or rare earth metals are a collection of seventeen chemical elements in the periodic table, namely scandium, yttrium, and the fifteen lanthanoids...
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