Scandium
| Topics: |
Geology (main)
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In 1879 a Swedish chemist named Lars Fredrik Nilson was looking for rare earth elements in the minerals euxenite and gadolinite when he discovered erbium and ytterbium; scandium was later separated from the ytterbium.
At that time these minerals had only been found in Scandinavia, and the element was named after the region. Scandium is a soft, silvery-white metallic element with an atomic number 21. It easily oxidizes and tarnishes to pink or yellow. When placed in water, a chemical reaction occurs which releases hydrogen. Scandium has some characteristics that are similar to the rare earth elements, and is often classified as a member of the group. The smaller size of its ion allows it to react chemically more like aluminum, Magnesium and zirconium.
| Previous Element: Calcium Next Element: Titanium |
| |
| Physical Properties | ||
|---|---|---|
| Color | silvery-white | |
| Phase at Room Temp. | solid | |
| Density (g/cm3) | 3.00 | |
| Hardness (Mohs) | --- | |
|
Melting Point (K) |
1812.2 | |
|
Boiling Point (K) |
3021 | |
| Heat of Fusion (kJ/mol) | 15.9 | |
| Heat of Vaporization (kJ/mol) | 305 | |
| Heat of Atomization (kJ/mol) | 378 | |
| Thermal Conductivity (J/m sec K) | 15.8 | |
| Electrical Conductivity (1/mohm cm) | 19.2 | |
| Source | U extract by-product | |
| Atomic Properties | ||
| Electron Configuration | [Ar]4s23d1 | |
|
Number of Isotopes |
28 (1 natural) | |
| Electron Affinity (kJ/mol) | 18.1 | |
| First Ionization Energy (kJ/mol) | 631 | |
| Second Ionization Energy (kJ/mol) | 1235 | |
| Third Ionization Energy (kJ/mol) | 2389 | |
| Electronegativity | 1.36 | |
| Polarizability (Å3) | 17.8 | |
| Atomic Weight | 44.956 | |
| Atomic Volume (cm3/mol) | 15 | |
| Ionic Radius2- (pm) | --- | |
| Ionic Radius1- (pm) | --- | |
| Atomic Radius (pm) | 163 | |
| Ionic Radius1+ (pm) | --- | |
| Ionic Radius2+ (pm) | --- | |
| Ionic Radius3+ (pm) | 88.5 | |
| Common Oxidation Numbers | +3 | |
| Other Oxid. Numbers | +1, +2 | |
| Abundance | ||
| In Earth's Crust (mg/kg) | 2.2×101 | |
| In Earth's Ocean (mg/L) | 2.4×10-4 | |
| In Human Body (%) | 0.00% | |
| Regulatory / Health | ||
| CAS Number | 7440-20-2 | |
| OSHA Permissible Exposure Limit (PEL) | No limit | |
| OSHA PEL Vacated 1989 | No limit | |
|
NIOSH Recommended Exposure Limit (REL) |
No limit | |
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Sources: |
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Scandium is more common in the sun and stars than on Earth. It is relatively rare on Earth, although it is more abundant than boron. Scandium is widely dispersed in minute quantities in the Earth’s crust. It is especially found in uranium minerals and trace amounts occur in iron and Magnesium rich rocks. One of the few minerals having a notable scandium content is thortveitite. But occurrences are rarely large enough to be exploited as an ore. Other rare minerals have scandium, bazzite, kolbeckite, ixiolite-Sc, perrierite-Sc, and magbasite. Norway, Madagascar, and the United States have thortveitite which contains from 44 to 48% scandium oxide (ScO2).
Scandium is very difficult to reduce to its pure state. In fact, it was not isolated in its pure form until 1937 and the first pound of pure scandium was not produced until 1960.
Contents
Name
The name scandium was derived from the Latin word Scandia which means Scandinavia.
Sources
Scandium has been recovered from mine tailings, particularly from tantalum deposits and uranium ore tailings. The majority of scandium production comes from thortveitite deposits. Processing the residues from mines with tantalum is another source of scandium. In the United States, scandium was recovered from thortveitite-rich mine tailings, like the tailings of the Crystal Mountain fluorite mine near Darby, Montana. Scandium also occurs in iron-Magnesium rocks and minerals in an abundance of 5 to 100 parts per million (ppm). If it could be mined, this would be enough of a resource to supply the world demand.
Worldwide, scandium resources are found in China, Kazakhstan, Madagascar, Norway and Russia. Scandium is in tin and tungsten deposits in China. In Russia, it is in the mineral apatite and associated with uranium deposits. In Norway, scandium is in large thortveitite deposits.
Geologists believe there are still significant deposits of scandium-bearing minerals yet to be discovered.
Uses
Scandium is used in mercury vapor lamps to create a light that is very much like natural sunlight. This is very important for camera lighting for producing movies and television shows. Scandium is also used in the manufacture of crystals for laser research and aerospace applications (Russia). Scandium is alloyed with aluminum and is used to make lightweight, strong sporting equipment like aluminum baseball bats, bicycle frames, and lacrosse sticks. There is some evidence that at high temperatures, it is possible to dissolve scandium in titanium to make a strong, heat-resistant metal alloy.
Toxicity
Based on its chemical similarities to the rare earths, scandium is not expected to present a serious health hazard.
Substitutes and Alternative Sources
There is no adequate substitute for scandium for its lighting and laser applications. Titanium, aluminum alloys and carbon fiber are a substitute for use in athletic equipment and sporting goods.
Further Reading
- Common Minerals and Their Uses, Mineral Information Institute.
- More than 170 Mineral Photographs, Mineral Information Institute.
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