Scandium is the chemical element with atomic number 21, symbol Sc.
It is a soft transition metal, silvery white in appearance. Scandium is found in
a few rare minerals from Scandinavia. It is classified with yttrium and
lanthanides in rare earths.
Scandium has 25 isotopes of mass number varying between 36 and 60, and 10 known
nuclear isomers. Among them, only 45Sc is stable and constitutes all the
scandium present in nature, making scandium both a monoisotopic element and a
mononucleidic element. Its standard atomic mass is 44.955912 (6)
Scandium is a soft, rare, trivalent, very light metallic element which becomes
yellowish or pink when exposed to air. This element has chemical properties
intermediate between those of aluminum and yttrium. The most common oxidation
state of scandium is +3.
World production is low, on the order of a few tonnes per year, and its price
high ($ 10,000 / kg).
By adding scandium iodide to a metal halide lamp, a light source spectrally
comparable to the Sun is obtained (color temperature of 4000 K - "neutral
white") which is used as a light source for night video or indoors.
The radioactive isotope 46Sc, due to its short half-life (84 days), is used as a
marker in petroleum refineries during cracking and for the detection of leaks
from pipelines.
Scandium with a melting point much higher than that of aluminum and almost as
light (density 2.9) is studied for possible aerospace applications.
The USSR has widely developed industrial scandium production and has optimized
an aluminum alloy containing 2% scandium, which considerably strengthens the
mechanical characteristics of aluminum. This alloy is commonly used in Russian
military aircraft construction. A complementary property of this alloy is that
it is weldable while this is not the case of a lithium aluminum alloy developed
in the West at the same time (this problem is now resolved) for equivalent
mechanical characteristics.
Scandium is the most powerful of the known anti-recrystallizers in aluminum.
This property is currently of interest to the aeronautical industry. It is used
at very low rates (less than 0.5%) to, for example, maintain a fiber texture
even after multiple heat treatments.
Scandium oxide (Sc2O3) can be used to protect optical surfaces because it is
very hard, resistant, UV transparent and fairly resistant to corrosion.
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rhenium germanium zirconium cadmium hafnium
barium lithium beryllium strontium calcium
Tantalum gadolinium samarium yttrium ytterbium
Lutetium praseodymium holmium erbium thulium dysprosium
terbium europium lanthanum cerium neodymium scandium
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