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Not to be confused with Scandinavium. ‹See Tfd›
"Element 21" redirects here. For the golf company, see Element 21 (company).
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Scandium in the periodic table
silvery white
General properties
Name, symbol, number scandium, Sc, 21
Pronunciation /ˈskændiəm/ SKAN-dee-əm
Element category transition metal
Group, period, block 3, 4, d
Standard atomic weight 44.955908(5)
Electron configuration [Ar] 3d1 4s2
2, 8, 9, 2
Physical properties
Phase solid
Density (near r.t.) 2.985 g·cm−3
Liquid density at m.p. 2.80 g·cm−3
Melting point 1814 K, 1541 °C, 2806 °F
Boiling point 3109 K, 2836 °C, 5136 °F
Heat of fusion 14.1 kJ·mol−1
Heat of vaporization 332.7 kJ·mol−1
Molar heat capacity 25.52 J·mol−1·K−1
Vapor pressure
Atomic properties
Oxidation states 3, 2,[1] 1[2]
(amphoteric oxide)
Electronegativity 1.36 (Pauling scale)
Ionization energies
1st: 633.1 kJ·mol−1
2nd: 1235.0 kJ·mol−1
3rd: 2388.6 kJ·mol−1
Atomic radius 162 pm
Covalent radius 170±7 pm
Van der Waals radius 211 pm
Crystal structure hexagonal close-packed
Scandium has a hexagonal close packed crystal structure
Magnetic ordering paramagnetic
Electrical resistivity (r.t.) (α, poly)
calc. 562 nΩ·m
Thermal conductivity 15.8 W·m−1·K−1
Thermal expansion (r.t.) (α, poly)
10.2 µm/(m·K)
Young's modulus 74.4 GPa
Shear modulus 29.1 GPa
Bulk modulus 56.6 GPa
Poisson ratio 0.279
Brinell hardness 750 MPa
CAS registry number 7440-20-2
Naming after Scandinavia
Prediction Dmitri Mendeleev (1871)
Discovery Lars Fredrik Nilson (1879)
First isolation Lars Fredrik Nilson (1879)
Most stable isotopes
Main article: Isotopes of scandium
iso NA half-life DM DE (MeV) DP
44m2Sc syn 58.61 h IT 0.2709 44Sc
γ 1.0, 1.1, 1.1 44Sc
ε - 44Ca
45Sc 100% 45Sc is stable with 24 neutrons
46Sc syn 83.79 d β 0.3569 46Ti
γ 0.889, 1.120 -
47Sc syn 3.3492 d β 0.44, 0.60 47Ti
γ 0.159 -
48Sc syn 43.67 h β 0.661 48Ti
γ 0.9, 1.3, 1.0 -
· references





Chemical characteristics of the element[edit]



Main article: Isotopes of scandium




In terms of earth's crust, 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.[6] However, scandium is distributed sparsely and occurs in trace amounts in many minerals.[7] Rare minerals from Scandinavia[8] and Madagascar[9] 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(III) oxide.[8]

The stable form of scandium is created in supernovas via the r-process.[10]



The production of metallic scandium is in the order of 10 kg per year.[11][12] The oxide is converted to scandium fluoride and reduced with metallic calcium.





Ionic radii (pm)
Al Sc Y La Lu
53.5 74.5 90.0 103.2 86.1

Oxides and hydroxides[edit]

The oxide Sc2O3 and the hydroxide Sc(OH)3 are amphoteric:[13]


The α- and γ- forms of scandium oxide hydroxide (ScO(OH)), are isostructural with their aluminium oxide hydroxide counterparts.[14] Solutions of Sc3+ in water are acidic because of hydrolysis.

Halides and pseudohalides[edit]


Organic derivatives[edit]


Uncommon oxidation states[edit]

Compounds that feature scandium in the oxidation state 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.[16] Scandium hydride is not well understood, although it appears not to be a saline hydride of Sc(II).[2] As is observed for most elements, a diatomic scandium hydride has been observed spectroscopically at high temperatures in the gas phase.[1] Scandium borides and carbides are non-stoichiometric, as is typical for neighboring elements.[17]


Dmitri Mendeleev, creator 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. Nilson prepared 2 grams of scandium oxide of high purity.[18][19] 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.[20]

Metallic scandium was produced for the first time in 1937 by electrolysis of a eutectic mixture, at 700–800 °C, of potassium, lithium, and scandium chlorides.[21] The first pound of 99% pure scandium metal was produced in 1960. The use for aluminium alloys began in 1971, following a US patent.[22] Aluminium-scandium alloys were also developed in the USSR.[23]

Laser crystals of gadolinium-scandium-gallium garnet (GSGG) were used in strategic defense applications developed in the Strategic Defense Initiative (SDI) in the 1980s and the 1990s.[24][25]


Parts of the MiG-29 are made from Al-Sc alloy.[26]

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 Al3Sc forms smaller crystals than are formed in other aluminium alloys[26] and the volume of precipitate-free zones that normally exist at the grain boundaries of age-hardening aluminium alloys is reduced.[26] Both of these effects increase the usefulness of the alloy.[why?] However, titanium alloys, which are similar in lightness and strength, are cheaper and much more widely used.[27]


Some items of sports equipment, which rely on high performance materials, have been made with scandium-aluminium alloys, including baseball bats,[28] and bicycle[29] frames and components. Lacrosse sticks are also made with scandium. The American firearm manufacturing company Smith & Wesson produces revolvers with frames composed of scandium alloy and cylinders of titanium or carbon steel.[30][31]

Dentists use erbium, chromium: yttrium-scandium-gallium garnet (Er,Cr:YSGG) lasers for cavity preparation and in endodontics.[32]

Approximately 20 kg (as Sc2O3) of scandium is used annually in the United States to make high-intensity discharge lamps.[33] Scandium iodide, along with sodium iodide, when added to a modified form of mercury-vapor lamp, produces a form of metal halide lamp. This lamp is a white light source with high color rendering index that sufficiently resembles sunlight to allow good color-reproduction with TV cameras.[34] 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 refineries as a tracing agent.[33] Scandium triflate is a catalytic Lewis acid used in organic chemistry.[35]

Health and safety[edit]

Elemental scandium is considered non-toxic and little animal testing of scandium compounds has been done.[36] The median lethal dose (LD50) levels for scandium(III) chloride for rats have been determined as 4 mg/kg for intraperitoneal and 755 mg/kg for oral administration.[37] In the light of these results compounds of scandium should be handled as compounds of moderate toxicity.

See also[edit]


  1. ^ a b McGuire, Joseph C.; Kempter, Charles P. (1960). "Preparation and Properties of Scandium Dihydride". Journal of Chemical Physics 33: 1584–1585. Bibcode:1960JChPh..33.1584M. doi:10.1063/1.1731452. 
  2. ^ a b Smith, R. E. (1973). "Diatomic Hydride and Deuteride Spectra of the Second Row Transition Metals". Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences 332 (1588): 113–127. Bibcode:1973RSPSA.332..113S. doi:10.1098/rspa.1973.0015. 
  3. ^ Gray, Theodore (2012) The Elements, Black Dog & Leventhal Publishers, p. 57, ISBN 1579128955.
  7. ^ Bernhard, F. (2001). "Scandium mineralization associated with hydrothermal lazurite-quartz veins in the Lower Austroalpie Grobgneis complex, East Alps, Austria". Mineral Deposits in the Beginning of the 21st Century. Lisse: Balkema. ISBN 90-265-1846-3. 
  8. ^ a b Kristiansen, Roy (2003). "Scandium – Mineraler I Norge". Stein (in Norwegian): 14–23. 
  9. ^ von Knorring, O.; Condliffe, E. (1987). "Mineralized pegmatites in Africa". Geological Journal 22: 253. doi:10.1002/gj.3350220619. 
  10. ^ Cameron, A.G.W. (June 1957). "Stellar Evolution, Nuclear Astrophysics, and Nucleogenesis". CRL-41. 
  11. ^ a b Deschamps, Y. "Scandium". Retrieved 2008-10-21. 
  12. ^ a b "Mineral Commodity Summaries 2008: Scandium". United States Geological Survey. Retrieved 2008-10-20. 
  14. ^ Christensen, A. Nørlund; Stig Jorgo Jensen (1967). "Hydrothermal Preparation of alpha-ScOOH and of gamma-ScOOH. Crystal Structure of alpha-ScOOH". Acta Chemica Scandinavica 21: 1121–126. doi:10.3891/acta.chem.scand.21-0121. 
  18. ^ Nilson, Lars Fredrik (1879). "Sur l'ytterbine, terre nouvelle de M. Marignac". Comptes Rendus (in French) 88: 642–647. 
  19. ^ Nilson, Lars Fredrik (1879). "Ueber Scandium, ein neues Erdmetall". Berichte der deutschen chemischen Gesellschaft (in German) 12 (1): 554–557. doi:10.1002/cber.187901201157. 
  20. ^ Cleve, Per Teodor (1879). "Sur le scandium". Comptes Rendus (in French) 89: 419–422. 
  21. ^ Fischer, Werner; Brünger, Karl; Grieneisen, Hans (1937). "Über das metallische Scandium". Zeitschrift für anorganische und allgemeine Chemie (in German) 231 (1–2): 54–62. doi:10.1002/zaac.19372310107. 
  23. ^ Zakharov, V. V. (2003). "Effect of Scandium on the Structure and Properties of Aluminum Alloys". Metal Science and Heat Treatment 45 (7/8): 246. doi:10.1023/A:1027368032062. 
  24. ^ Hedrick, James B. "Scandium". REEhandbook. Retrieved 2012-05-09. 
  26. ^ a b c d Ahmad, Zaki (2003). "The properties and application of scandium-reinforced aluminum". JOM 55 (2): 35. Bibcode:2003JOM....55b..35A. doi:10.1007/s11837-003-0224-6. 
  27. ^ Schwarz, James A.; Contescu, Cristian I.; Putyera, Karol (2004). Dekker encyclopédia of nanoscience and nanotechnology, Volume 3. CRC Press. p. 2274. ISBN 0-8247-5049-7. 
  28. ^ Bjerklie, Steve (2006). "A batty business: Anodized metal bats have revolutionized baseball. But are finishers losing the sweet spot?". Metal Finishing 104 (4): 61. doi:10.1016/S0026-0576(06)80099-1. 
  29. ^ "Easton Technology Report : Materials / Scandium". Retrieved 2009-04-03. 
  33. ^ a b Hammond, C.R. in CRC Handbook of Chemistry and Physics 85th ed., Section 4; The Elements
  35. ^ Kobayashi, Shu; Manabe, Kei (2000). "Green Lewis acid catalysis in organic synthesis". Pure Appl. Chem. 72 (7): 1373–1380. doi:10.1351/pac200072071373. 
  37. ^ Haley, Thomas J.; Komesu, L.; Mavis, N.; Cawthorne, J.; Upham, H. C. (1962). "Pharmacology and toxicology of scandium chloride". Journal of Pharmaceutical Sciences 51 (11): 1043–5. doi:10.1002/jps.2600511107. PMID 13952089. 

Further reading[edit]

External links[edit]