Scandium is a chemical element with the symbol Sc and atomic number 21. It is a silvery-white metallic d-block element. Historically, it has been classified as a rare-earth element, together with yttrium and the lanthanides. It was discovered in 1879 by spectral analysis of the minerals euxenite and gadolinite from Scandinavia. Scandium is present in most of the deposits of rare-earth and uranium compounds, but it is extracted from these ores in only a few mines worldwide. Because of the low availability and difficulties in the preparation of metallic scandium, which was first done in 1937, applications for scandium were not developed until the 1970s, when the positive effects of scandium on aluminium alloys were discovered. To this day, its use in such alloys remains its only major application. The global trade of scandium oxide is 15–20 tonnes per year. The properties of scandium compounds are intermediate between those of aluminium and yttrium. A diagonal relationship exists between the behavior of magnesium and scandium, just as there is between beryllium and aluminium. In the chemical compounds of the elements in group 3, the predominant oxidation state is +3.
21ScScandium
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Atomic properties
Standard atomic weight | 44.9559 ±4·10-6 |
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Atomic mass | 44.9559 u |
Atomic radii
Radius (empirical) | 162 pm |
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Radius (calculated) | 184 pm |
Covalent radius | 170 ±7 pm |
Van der Waals radius | 211 pm |
Atomic shell
Electron configuration | Ar 3d1 4s2 |
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Ionization energy | (1st) 6.56149 eV (2nd) 12.79977 eV (3rd) 24.756838 eV (4th) 73.4894 eV (5th) 91.95 eV |
Shell model | Electrons k-shell:2 l-shell:8 m-shell:9 n-shell:2 |
Physical properties
Phase | solid |
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Density | 2.985 g·cm−3 |
Molar volume | 1.5·10-5 m3·mol−1 |
Temperatures
Melting point | 1,814 K |
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Boiling point | 3,109 K |
Liquid range | 1,295 K |
Transition temperature | 0.34 K |
Enthalpies
Melting enthalpy | 16 kJ·mol-1 |
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Enthalpy of vaporization | 318 kJ·mol-1 |
Binding energy | 378 kJ·mol-1 |
Heat and conductivity
Specific heat capacity | 586 J·kg−1·K−1 |
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Thermal conductivity | 16 W·m-1·K-1 |
Expansion coefficient | 1.02·10-5 K-1 |
Hardnesses
Mohs hardness | 2.5 |
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Brinell hardness | 750 NM·m-2 |
Elastic properties
Young’s modulus | 74 GPa |
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Shear modulus | 29 GPa |
Bulk modulus | 57 GPa |
Poisson’s ratio | 0.28 |
Electrical properties
Electrical conductivity | 1.81·106 S·m-1 |
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Resistance | 5.5·10-7 Ωm |
Magnetism
Magnetism | paramagnetic |
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Magnetic susceptibility | 3.15·10-4 cm3·mol−1 (292 K) |
Chemical properties
Basicity | slightly basic |
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Oxidation state | 3 |
Standard potential | -2.03 V (Sc3+ + 3e- → Sc) |
Electronegativity
Pauling scale | 1.36 |
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Sanderson scale | 1.02 |
Allred-Rochow scale | 1.2 |
Ghosh-Gupta scale | 2.857 eV |
Nagle scale | 1.17 |
Pearson absolute negativity | 3.34 eV |
Other properties
Natural occurrence | primordial |
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Crystal structure | Hexagonal close-packed |
Goldschmidt Classification | lithophile |
Superconductor | with transition tempperature under special conditions |
Price/kg | 3,460 USD |
Natural abundances
satellite_alt
Universe
30 ppb ≈ 3.01·1011 M☉
sunny
Sun
40 ppb ≈ 7.95·1010 Mt
destruction
Meteorite
6,500 ppb ≈ 6.5 g
public
Earth’s crust
26,000 ppb ≈ 720,000 Mt
water_drop
Oceans
0.0015 ppb ≈ 2.05 kt
waves
Flowing water
0.004 ppb ≈ 64 t
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