 |
|
| A B C D E F G H I J K L M N O P Q R S T U V W X Y Z |
|
|
aluminum (Al)
 |
Aluminum is extremely useful for several reasons. First, it is light – weighing only about a third as much as other common metals for the same volume. It is also strong, and to give the same rigidity need weigh only half as much as steel. Its strength can be greatly increased by alloying with other metals.
Second, although aluminum combines readily with other elements, including oxygen, it does not rust or corrode in the air, because a thin film of oxide is formed on the surface, and this protects the metal below. So aluminum has excellent corrosion resistance.
Third, aluminum conducts heat and electricity extremely well. An aluminum wire will conduct only 60 percent as much electricity as a copper wire of the same size, but more than twice as much as a copper wire of the same weight. Its good heat conducting qualities and its resistance to corrosion have ed to its widespread use in cooking vessels.
| atomic number | 13 |
| relative atomic mass | 26.98154 |
| electron configuration | 1s22s22p63s23p1 |
| atomic radius | 143.1 pm |
| oxidation state | 3 |
| melting point | 660.3 °C (1,220.6 °F) |
| boiling point | 2,519 °C (4,566 °F) |
| relative density | 2.69 |
Discovery and extraction
Compounds of aluminum have been known for centuries, but the metal was first made from these by Humphry Davy. The metallic aluminum he produced was too impure for him to have any real idea of its properties, and a purer metal was first made by the Danish chemist Hans Ørsted in Copenhagen in 1825 and the German chemist Friedrich Wöhler in 1827. It was not until 1845 that Wöhler succeeded in producing a sufficient quantity to discover that it was a very light metal which was malleable.
In succeeding years ways were discovered of making larger quantities of aluminum through electrolysis – that is, by passing an electric current through a fused or liquefied aluminum compound. But the metal remained very expensive, and it was only in 1886 that the French chemist Hèroult and the American C. M. Hall discovered at about the same time the method of making aluminum on a larger scale, now known as the Hall process, which is still used. This is by electrolysis of alumina (aluminum oxide) dissolved in a bath of fused cryolite (sodium aluminum fluoride).
Duralim
One of the most important alloys of aluminum is duralim, an alloy containing about 4 percent copper with smaller quantities of manganese, magnesium, and silicon. It was invented in 1908 by a German engineer, Wilm. This alloy has been very important in the development of aviation owing to its combination of strength and lightness. It is not as resistant to corrosion as pure aluminum, but when high corrosion resistance is needed it can be coated ob both sides with a layer of pure aluminum.
Related category
• INORGANIC CHEMISTRY
Also on this site:
Encyclopedia of Alternative Energy & Sustainable Living
Encyclopedia of History
Transport Concepts & Designs (partner site)