Scandium

Scandium is a chemical element with the symbol Sc and atomic number 21. It is a shiny, silvery-white metal found in the d-block of the periodic table. It is usually called a rare-earth element, along with yttrium and the lanthanides.

Scandium was discovered in 1879 by studying two minerals, euxenite and gadolinite, from Scandinavia.

Scandium is found in many places with rare-earth and uranium materials, but only a few mines around the world take it from these ores. It was hard to make scandium metal until 1937, and people did not find many uses for it until the 1970s. They then learned that scandium could make aluminium stronger. Today, this is its most common use.

Scandium compounds act a bit like those of aluminium and yttrium. Scandium and magnesium also behave similarly, just as beryllium and aluminium do. In its compounds, scandium usually has an oxidation state of +3.

Properties

Scandium is a soft, silvery metal that can change color a little when it touches air. It slowly dissolves in many common acids but does not dissolve in a special mix of two acids. Tiny pieces of scandium can catch fire in air and burn with a bright yellow flame.

Scandium is most commonly found as one type called ⁴⁵Sc. Scientists have found many other types of scandium, but they are not stable and break down over time. In the Earth’s crust, scandium is not rare but is spread out and found only in small amounts in different minerals. Some minerals from places like Scandinavia and Madagascar contain more scandium, but these are also sources of other rare elements.

Production

The world makes about 15 to 20 tonnes of scandium each year, mostly as scandium oxide. The amount we make and need is growing. Scandium is usually found when we mine other elements like uranium, iron, or rare earth metals.

To get pure scandium metal, we first change the oxide into scandium fluoride and then use calcium metal to turn it into scandium.

Madagascar and a region in Norway have minerals with a lot of scandium, but we don’t mine them much yet. Adding a tiny amount of scandium to aluminium can make it stronger. Scandium is also used in special cells that can produce energy very well.

Compounds

See also the categories Scandium compounds and Scandium minerals

Scandium mostly forms compounds where it has a +3 charge. Because of this, scandium behaves more like yttrium than aluminium. This is why scandium is often grouped with elements called lanthanides.

Oxides and hydroxides

The oxide Sc₂O₃ and the hydroxide Sc(OH)₃ can react with both acids and bases. When mixed with a base, they form a scandate ion. When mixed with an acid, they form another compound.

Halides and pseudohalides

The compounds ScX₃, where X stands for chlorine, bromine, or iodine, dissolve easily in water. However, ScF₃ does not dissolve. These compounds can act as Lewis acids.

Organic derivatives

Main article: Organoscandium chemistry

Scandium can form compounds with organic molecules, similar to lanthanides. One example is a compound with cyclopentadienyl ligands.

Uncommon oxidation states

It is rare, but scandium can form compounds with charges other than +3. For example, there is a compound called CsScCl₃ where scandium has a +2 charge. Scandium can also form compounds with hydrogen and other elements in different charges.

History

Dmitri Mendeleev created the periodic table and guessed that an element called ekaboron might exist between elements with an atomic mass of 40 and 48, in 1869. In 1879, Lars Fredrik Nilson and his team found this element in minerals called euxenite and gadolinite. Nilson made 2 grams of pure scandium oxide and named the element scandium after Scandinavia. Another scientist, Per Teodor Cleve, saw that Nilson's discovery matched Mendeleev’s prediction and told Mendeleev about it.

In 1937, people made metallic scandium for the first time using a special process called electrolysis. The first pound of very pure scandium metal was made in 1960. In 1971, people began mixing scandium with aluminium to make strong alloys, first in the USSR. Later, in the 1980s and 1990s, special crystals made from scandium were used for important projects.

Applications

Aluminium alloys

Main article: Aluminium–scandium alloys

Scandium is mostly used to make special aluminium alloys. These alloys are important for aircraft parts. They contain a small amount of scandium, between 0.1% and 0.5%. They have been used in Russian military planes like the Mikoyan-Gurevich MiG-21 and MiG-29.

Adding scandium to aluminium makes the metal stronger, especially when it is welded. It forms tiny crystals that make the aluminium harder without making it heavier. This keeps the alloys strong and light, which is useful for aircraft and other special parts.

Some sports gear, like baseball bats, tent poles, bicycle frames, and components, are made from these alloys. Lacrosse sticks also use scandium. A company called Smith & Wesson makes guns with parts from scandium alloys.

Light sources

Scandium is used to make bright lights called metal-halide lamps. These lamps look like sunlight and are good for TV cameras. Dentists use special lasers with scandium to treat teeth.

Other

A special kind of scandium can track oil in refineries. Scandium is also used in chemistry for some reactions. It has been studied for very accurate clocks and for energy cells that can use many fuels.

Health and safety

Elemental scandium is not known to be harmful, but we don’t have many tests to be sure. Scientists have studied scandium chloride and found that large amounts can be harmful to rats. Because of this, we should treat scandium compounds as possibly dangerous. The body handles scandium in a way that is similar to gallium, which can cause problems if it is not dissolved well.