Sc - ScandiumSee metal norms for Scandium
|Chemical Element||Scandium||Melting Point °C||1541|
|Chemical Symbol||Sc||Boiling Point °C||2831|
|Atomic Number||21||Density g/cm3||3|
Scandium is a soft, silvery, yellow-white metal and a member of Group 3 of the Periodic Table, heading a list of 10 metals called the First Row Transition Elements. Scandium is the 35th most abundant element in the Earth’s crust. It tarnishes in air and burns easily once it has been ignited. It reacts with water to form hydrogen gas and will dissolve in many acids. Scandium is a very lightweight metal with a fairly high melting point and good resistance to corrosion. It is also a rare metal, not because it is hard to find, but because it is hard to find in a large concentration (i.e. an ore), and is thinly distributed around the world (0.0025% of the Earth’s crust), so collecting and purifying the substance is expensive and time-consuming. Interestingly, scandium is found in greater concentrations in the sun and certain other stars.
Scandium is one of the elements that Dimitri Mendeleyev predicted when devising his Periodic Table in 1869. Mendeleyev noticed that there was a gap in atomic weights between calcium (40) and titanium (48) and he, therefore, predicted the existence of scandium (44). It was not until 10 years later that this prediction was confirmed by Lars Frederick Nilson, who was at the time a Professor of Analytical Chemistry at the University of Uppsala, Sweden. Whilst analysing a mineral named euxenite, Nilson was able to extract erbium oxide, from which he then extracted ytterbium oxide and another oxide which he could not determine. By analysing the atomic spectrum of these oxides, he was able to determine that the unknown oxide was in fact the oxide of a new element. He then determined that this new element had an atomic weight of 44 and showed that its oxide was of the form Sc2O3. The new element was named scandium, as Nilson believed that the mineral euxenite from which he had extracted scandium was only found in Scandinavia. Nilson did not live to see his new element in its pure form, as it was not until 1937 that a sample of scandium was produced using electrolysis of molten scandium chloride dissolved in a melt of other metal chlorides. The discovery of scandium led to widespread acceptance of the predictive power of the Periodic Table.
While resources of scandium are relatively abundant, it is widely dispersed in minute quantities. World primary production of scandium is thought to be in the order of only a few tonnes per year, of which approximately 1% is converted into the metal. This figure is vague because of the lack of accurate data from Chinese rare earth mines. Although scandium is not mined in quantity, sufficient amounts to meet demand are available in tailings. The majority of scandium metal comes from the military stockpiles (extracted from uranium tailings) in Kazakhstan and other former Soviet countries.
Consumption is in the order of 5,000 KG/year, and typically is employed in aluminium alloys as a grain refiner. The original use of scandium-aluminium alloys was in nose cones for Soviet submarine-launched ballistic missiles since it allowed the missile to pierce through the Arctic ice-cap (from beneath) without incurring any damage.
Today, aluminium-scandium alloys are mostly used for minor aerospace industry components and for high-quality sports equipment. Scandium alloys are especially desirable for use in, for example, baseball bats, lacrosse sticks, and bicycle frames. Small amounts of scandium are also used in high-intensity lights and fuel cells, as well as in firearms.
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- Stwertka, Albert. A Guide to the Elements, 3rd Edition, Oxford University Press, 2012