Difference between revisions of "Scandium" - New World Encyclopedia
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− | '''Scandium''' (chemical symbol '''Sc''', [[atomic number]] 21) is a soft, silvery, white [[metal]]. Scandium ore occurs in rare minerals from [[Scandinavia]] and elsewhere. It is sometimes considered along with [[yttrium]] and the [[lanthanide]]s and [[ | + | '''Scandium''' (chemical symbol '''Sc''', [[atomic number]] 21) is a soft, silvery, white [[metal]]. Scandium ore occurs in rare minerals from [[Scandinavia]] and elsewhere. It is sometimes considered along with [[yttrium]] and the [[lanthanide]]s and [[actinide]]s, to be a [[rare earth]]. |
== Occurrence and isolation == | == Occurrence and isolation == | ||
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== Notable characteristics == | == Notable characteristics == | ||
− | Scandium is | + | Scandium is situated between [[calcium]] and [[titanium]] in period 4 of the [[periodic table]]. It is the first [[transition metal]] in period 4. In addition, it lies at the top of group 3 (former group 3B), just above yttrium. Chemically, it resembles yttrium (and the rare earth metals) more than it resembles titanium. |
− | + | ||
+ | Silvery when pure, scandium develops a slightly yellowish or pinkish cast when exposed to air. It is a soft, light metal. It is resistant to corrosion by acids. For example, it is not attacked by a 1:1 mixture of [[nitric acid]]([[hydrogen|H]][[nitrogen|N]][[oxygen|O]]<sub>3</sub>) and hydrofluoric acid ([[hydrogen|H]][[fluorine|F]]). | ||
+ | |||
+ | In most of its compounds, the [[oxidation state]] of scandium is +3. Thus scandium is sometimes seen as the oxide, Sc<sub>2</sub>0<sub>3</sub>, or the chloride, ScCl<sub>3</sub>. | ||
=== Isotopes === | === Isotopes === | ||
− | Naturally occurring scandium is composed of | + | Naturally occurring scandium is composed of one stable [[isotope]], <sup>45</sup>Sc. In addition, many [[radioactive]] isotopes have been produced artificially, with atomic mass numbers ranging from 36 to 60. The three most stable radioisotopes are: <sup>46</sup>Sc, with a [[half-life]]* of 83.8 days; <sup>47</sup>Sc, with a half-life of 3.35 days; and <sup>48</sup>Sc, with a half-life of 43.7 hours. 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. |
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== Compounds == | == Compounds == | ||
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==References== | ==References== | ||
+ | * Greenwood, N.N.; and Earnshaw, A. (1998). Chemistry of the Elements (2nd Edition). New York: Elsevier. Online version available at [http://www.knovel.com/knovel2/Toc.jsp?BookID=402&VerticalID=0], accessed on November 29, 2006. | ||
* Cotton, F. Albert; and Wilkinson, Geoffrey (1980), ''Advanced Inorganic Chemistry'' (4th ed.), New York: Wiley. ISBN 0-471-02775-8. | * Cotton, F. Albert; and Wilkinson, Geoffrey (1980), ''Advanced Inorganic Chemistry'' (4th ed.), New York: Wiley. ISBN 0-471-02775-8. | ||
* [http://periodic.lanl.gov/elements/21.html Scandium] Los Alamos National Laboratory. Accessed on November 29, 2006. | * [http://periodic.lanl.gov/elements/21.html Scandium] Los Alamos National Laboratory. Accessed on November 29, 2006. |
Revision as of 16:36, 29 November 2006
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Name, Symbol, Number | scandium, Sc, 21 | |||||||||||||||||||||||||||||||||||||||||||||||||||
Chemical series | transition metals | |||||||||||||||||||||||||||||||||||||||||||||||||||
Group, Period, Block | 3, 4, d | |||||||||||||||||||||||||||||||||||||||||||||||||||
Appearance | silvery white | |||||||||||||||||||||||||||||||||||||||||||||||||||
Atomic mass | 44.955912(6) g/mol | |||||||||||||||||||||||||||||||||||||||||||||||||||
Electron configuration | [Ar] 3d1 4s2 | |||||||||||||||||||||||||||||||||||||||||||||||||||
Electrons per shell | 2, 8, 9, 2 | |||||||||||||||||||||||||||||||||||||||||||||||||||
Physical properties | ||||||||||||||||||||||||||||||||||||||||||||||||||||
Phase | solid | |||||||||||||||||||||||||||||||||||||||||||||||||||
Density (near r.t.) | 2.985 g/cm³ | |||||||||||||||||||||||||||||||||||||||||||||||||||
Liquid density at m.p. | 2.80 g/cm³ | |||||||||||||||||||||||||||||||||||||||||||||||||||
Melting point | 1814 K (1541 °C, 2806 °F) | |||||||||||||||||||||||||||||||||||||||||||||||||||
Boiling point | 3109 K (2836 °C, 5136 °F) | |||||||||||||||||||||||||||||||||||||||||||||||||||
Heat of fusion | 14.1 kJ/mol | |||||||||||||||||||||||||||||||||||||||||||||||||||
Heat of vaporization | 332.7 kJ/mol | |||||||||||||||||||||||||||||||||||||||||||||||||||
Heat capacity | (25 °C) 25.52 J/(mol·K) | |||||||||||||||||||||||||||||||||||||||||||||||||||
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Atomic properties | ||||||||||||||||||||||||||||||||||||||||||||||||||||
Crystal structure | hexagonal | |||||||||||||||||||||||||||||||||||||||||||||||||||
Oxidation states | 3 (weakly basic oxide) | |||||||||||||||||||||||||||||||||||||||||||||||||||
Electronegativity | 1.36 (Pauling scale) | |||||||||||||||||||||||||||||||||||||||||||||||||||
Ionization energies (more) |
1st: 633.1 kJ/mol | |||||||||||||||||||||||||||||||||||||||||||||||||||
2nd: 1235.0 kJ/mol | ||||||||||||||||||||||||||||||||||||||||||||||||||||
3rd: 2388.6 kJ/mol | ||||||||||||||||||||||||||||||||||||||||||||||||||||
Atomic radius | 160 pm | |||||||||||||||||||||||||||||||||||||||||||||||||||
Atomic radius (calc.) | 184 pm | |||||||||||||||||||||||||||||||||||||||||||||||||||
Covalent radius | 144 pm | |||||||||||||||||||||||||||||||||||||||||||||||||||
Miscellaneous | ||||||||||||||||||||||||||||||||||||||||||||||||||||
Magnetic ordering | ??? | |||||||||||||||||||||||||||||||||||||||||||||||||||
Electrical resistivity | (r.t.) (α, poly) calc. 562 nΩ·m | |||||||||||||||||||||||||||||||||||||||||||||||||||
Thermal conductivity | (300 K) 15.8 W/(m·K) | |||||||||||||||||||||||||||||||||||||||||||||||||||
Thermal expansion | (r.t.) (α, poly) 10.2 µm/(m·K) | |||||||||||||||||||||||||||||||||||||||||||||||||||
Speed of sound (thin rod) | (r.t.) 74.4 m/s | |||||||||||||||||||||||||||||||||||||||||||||||||||
Shear modulus | 29.1 GPa | |||||||||||||||||||||||||||||||||||||||||||||||||||
Bulk modulus | 56.6 GPa | |||||||||||||||||||||||||||||||||||||||||||||||||||
Poisson ratio | 0.279 | |||||||||||||||||||||||||||||||||||||||||||||||||||
Brinell hardness | 750 MPa | |||||||||||||||||||||||||||||||||||||||||||||||||||
CAS registry number | 7440-20-2 | |||||||||||||||||||||||||||||||||||||||||||||||||||
Notable isotopes | ||||||||||||||||||||||||||||||||||||||||||||||||||||
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Scandium (chemical symbol Sc, atomic number 21) is a soft, silvery, white metal. Scandium ore occurs in rare minerals from Scandinavia and elsewhere. It is sometimes considered along with yttrium and the lanthanides and actinides, to be a rare earth.
Occurrence and isolation
Scandium is distributed sparsely on Earth, occurring only as trace quantities in various minerals. It is never found as a free metal. Rare minerals from Scandinavia and Madagascar—such as thortveitite, euxenite, and gadolinite—are the only known concentrated sources of this element. It is also found in residues that remain after tungsten is extracted from wolframite, and in the byproducts of uranium-mill tailings.
Scandium is more common in the Sun and certain stars than on Earth. It is only the fiftieth most common element on Earth (thirty-fifth most abundant in the Earth's crust), but it is the twenty-third most common element in the Sun.
The blue color of the aquamarine variety of beryl is thought to be produced by the presence of scandium impurities in it.
The present main source of scandium metal is from military stockpiles in parts of the former Soviet Union (mainly in Ukraine), which were themselves obtained from uranium tailings. There is no primary production in the Americas, Europe, or Australia.
History
In 1869, Dmitri Mendeleev used his periodic law to predict the existence and some properties of three unknown elements, including one that he called ekaboron.
Apparently unaware of that prediction, Lars Fredrick Nilson and his team were looking for rare earth metals in the spring of 1879. Using spectral analysis, they found a new element in the minerals euxenite and gadolinite. They named it scandium, from the Latin word Scandia meaning "Scandinavia." In attempting to isolate scandium, they processed 10 kilograms of euxenite and produced about 2.0 grams of a very pure scandium oxide (Sc2O3).
Per Teodor Cleve of Sweden concluded that scandium corresponded well to the hoped-for ekaboron, and he notified Mendeleev of this in August.
Fischer, Brunger, and Grienelaus prepared metallic scandium for the first time in 1937. They performed electrolysis of a molten combination of potassium, lithium, and scandium chlorides, at a temperature of 700 to 800°C. Tungsten wires in a pool of liquid zinc were the electrodes in a graphite crucible. The first pound of 99% pure scandium metal was not produced until 1960.
Notable characteristics
Scandium is situated between calcium and titanium in period 4 of the periodic table. It is the first transition metal in period 4. In addition, it lies at the top of group 3 (former group 3B), just above yttrium. Chemically, it resembles yttrium (and the rare earth metals) more than it resembles titanium.
Silvery when pure, scandium develops a slightly yellowish or pinkish cast when exposed to air. It is a soft, light metal. It is resistant to corrosion by acids. For example, it is not attacked by a 1:1 mixture of nitric acid(HNO3) and hydrofluoric acid (HF).
In most of its compounds, the oxidation state of scandium is +3. Thus scandium is sometimes seen as the oxide, Sc203, or the chloride, ScCl3.
Isotopes
Naturally occurring scandium is composed of one stable isotope, 45Sc. In addition, many radioactive isotopes have been produced artificially, with atomic mass numbers ranging from 36 to 60. The three most stable radioisotopes are: 46Sc, with a half-life of 83.8 days; 47Sc, with a half-life of 3.35 days; and 48Sc, with a half-life of 43.7 hours. 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.
Compounds
- See also Scandium compounds.
Applications
Since it is a very rare metal, scandium doesn't have many applications. If it were more common, it might be useful in the making of aircraft and spacecraft structures, probably alloyed with other metals.
It is also used in various lacrosse sticks. The light yet strong metal is need for precise accuracy and speed.
Approximately 20 kg (as Sc2O3) of scandium is used annually in the United States to make high-intensity lights. [1] Scandium iodide added to mercury-vapor lamps produces an efficient artificial light source that resembles sunlight, and which allows good color-reproduction with TV cameras. About 80 kg of scandium is used in light bulbs globally per year. The radioactive isotope Sc-46 is used in oil refineries as a tracing agent. [1]
The main application of scandium by weight is in aluminium-scandium alloys for minor aerospace industry components, and for unusual designs sports equipment (bikes, baseball bats, firearms, etc.) which rely on high performance materials. However, titanium, being much more common, and similar in lightness and strength, is much more widely used, with tons found in some aircraft, especially military ones.
When added to aluminium, scandium substantially lowers the rate of recrystallization and associated grain-growth in weld heat-affected zones. Aluminium, being a face-centred-cubic metal, is not particularly subject to the strengthening effects of the decrease in grain diameter. However, the presence of fine dispersions of Al3Sc does increase strength by a small measure, much as any other precipitate system in aluminium alloys. It is added to aluminum alloys primarily to control that otherwise excessive grain growth in the heat-affected zone of weldable structural aluminium alloys, which gives two knock-on effects; greater strengthening via finer precipitation of other alloying elements and by reducing the precipitate-free zones that normally exist at the grain boundaries of age-hardening aluminium alloys.
The original use of scandium-aluminium alloys was in the nose cones of some USSR submarine-launched ballistic missiles (SLBMs). The strength of the resulting nose cone was enough to enable it to pierce the ice-cap without damage, and so, enabling a missile launch while still submerged under the Arctic ice cap.
See also
- Scandium compounds
- Scandium minerals
Footnotes
ReferencesISBN links support NWE through referral fees
- Greenwood, N.N.; and Earnshaw, A. (1998). Chemistry of the Elements (2nd Edition). New York: Elsevier. Online version available at [1], accessed on November 29, 2006.
- Cotton, F. Albert; and Wilkinson, Geoffrey (1980), Advanced Inorganic Chemistry (4th ed.), New York: Wiley. ISBN 0-471-02775-8.
- Scandium Los Alamos National Laboratory. Accessed on November 29, 2006.
- Scandium SPECTRUM Chemical Fact Sheet. Accessed on November 29, 2006.
External links
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