Scandium
Scandium is present in most of the deposits of rare earth and uranium compounds, but it is extracted from these ores in only a few mines worldwide. Because of the low availability and the difficulties in the preparation of metallic scandium, which was first done in 1937, it took until the 1970s before applications for scandium were developed. The positive effects of scandium on aluminium alloys were discovered in the 1970s, and its use in such alloys remains its only major application. The global trade of the pure metal is around a hundred pounds a year on average.
The properties of scandium compounds are intermediate between those of aluminium and yttrium. A diagonal relationship exists between the behavior of magnesium and scandium, just as there is between beryllium and aluminium. In the chemical compounds of the elements shown as group 3, above, the predominant oxidation state is +3.
Occurrence
In terms of earth's crust, scandium is not particularly rare. Estimates vary from 18 to 25 ppm, which is comparable to the abundance of cobalt (20–30 ppm). Scandium is only the 50th most common element on earth (35th most abundant in the crust), but it is the 23rd most common element in the Sun. However, scandium is distributed sparsely and occurs in trace amounts in many minerals. Rare minerals from Scandinavia and Madagascar such as thortveitite, euxenite, and gadolinite are the only known concentrated sources of this element. Thortveitite can contain up to 45% of scandium in the form of scandium(III) oxide.
The stable form of scandium is created in supernovas via the r-process.
| Symbol | Sc | |
| Atomic Number | 21 | |
| Atomic Weight | 44.95591 | |
| Oxidation States | +3 | |
| Electronegativity, Pauling | 1.36 | |
| State at RT | Solid, Metal | |
| Melting Point, K | 1814 | |
| Boiling Point, K | 3104 |
Appearance and Characteristics
Harmful effects:
Scandium is considered to be of low toxicity.
Characteristics:
- Scandium is a soft, light, silvery-white metal, which becomes slightly tinged with yellow or pink when exposed to air.
- Scandium is almost as light (low density) as aluminum but it has a much higher melting point.
- It is therefore of potential specialty use in aircraft – scandium will not be used generally because it is much more expensive than aluminum.
- Scandium reacts with many acids.
- When present in compounds, scandium exists usually in the trivalent state, Sc3+.
- Its oxide is white and most of its salts are colorless.
Uses of Scandium
- Scandium is used in aluminum-scandium alloys for aerospace industry components and for sports equipment such as bicycle frames, fishing rods, golf iron shafts and baseball bats.
- Scandium iodide is used in mercury vapor lamps, which are used to replicate sunlight in studios for the film and television industry. Scandium oxide (scandia), is used to make high intensity “stadium” lights.
- The radioactive isotope 45Sc is used in oil refineries as a tracing agent.
- Very dilute scandium sulfate is used to improve the germination of seeds such as corn, peas and wheat.
