Scandium

March 1, 2011, 5:46 pm
Content Cover Image

Ultrapure crystalline scandium, 5 grams. Original size 2 cm. Source: images-of-elements.com

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.

caption Scandium. (Source: University of Texas)

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
21

Sc

44.956
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
Sources:
Mineral Information Institute
Jefferson Accelerator Laboratory
EnvironmentalChemistry.com
 

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.

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

 

 

Disclaimer: This article is taken wholly from, or contains information that was originally published by, the Mineral Information Institute. Topic editors and authors for the Encyclopedia of Earth may have edited its content or added new information. The use of information from the Mineral Information Institute should not be construed as support for or endorsement by that organization for any new information added by EoE personnel, or for any editing of the original content.

 

Glossary

Citation

Institute, M. (2011). Scandium. Retrieved from http://www.eoearth.org/view/article/155882

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