|
For stadium lighting.
| Atomic Number: |
21 |
| Atomic Symbol: |
Sc |
| Atomic Weight: |
44.9559 |
| Electron Configuration: |
[Ar]4s23d1 |
History
(L. Scandia, Scandinavia) On the basis of the Periodic System, Mendeleev predicted the
existence of ekaboron, which would have an atomic weight between 40 of calcium and 48 of
titanium.
The element was discovered by Nilson in 1878 in the minerals euxenite and gadolinite,
which had not yet been found anywhere except in Scandinavia. By processing 10 kg of
euxenite and other residues of rare-earth minerals, Nilson was able to prepare about 2g of
highly pure scandium oxide. Later scientists pointed out that Nilson's scandium was
identical with Mendeleev's ekaboron.
Sources
Scandium is apparently much more abundant (the 23rd most) in the sun and certain stars
than on earth (the 50th most abundant). It is widely distributed on earth, occurring in
very minute quantities in over 800 mineral species. The blue color of beryl (aquamarine
variety) is said to be due to scandium. It occurs as a principal component in the rare
mineral thortveitite, found in Scandinavia and Malagasy. It is also found in the residues
remaining after the extraction of tungsten from Zinnwald wolframite, and in wiikite and
bazzite.
Most scandium is presently being recovered from thortveitite or is extracted as a
by-product from uranium mill tailings. Metallic scandium was first prepared in 1937 by
Fischer, Brunger, and Grienelaus who electrolyzed a eutectic melt of potassium
lithium,and scandium chlorides at 700 to 800oC. Tungsten wire and a pool of molten zinc
served as the electrodes in a graphite crucible. Pure scandium is now produced by reducing
scandium fluoride with calcium metal.
The production of the first pound of 99% pure scandium metal was announced in 1960.
Properties
Scandium is a silver-white metal which develops a slightly yellowish or pinkish cast
upon exposure to air. A relatively soft element, scandium resembles yttrium and the
rare-earth metals more than it resembles aluminum or
titanium.
It is a very light metal and has a much higher melting point than aluminum, making it of interest to designers of
spacecraft. Scandium is not attacked by a 1:1 mixture of HNO3 and 48% HF.
Costs
Scandium oxide costs about $75/g.
Uses
About 20 kg of scandium (as Sc2O3) are now being used yearly in
the U.S. to produce high-intensity lights, and the radioactive isotope 46Sc is used as a
tracing agent in refinery crackers for crude oil, etc.
Scandium iodide added to mercury vapor lamps produces a highly efficient light source
resembling sunlight, which is important for indoor or night-time color TV.
Handling
Little is yet known about the toxicity of scandium; therefore it should be handled with
care.
|
