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Physical Properties
Aluminum is soft and lightweight with a dull silvery appearance due to a thin layer of oxidation that forms when it is exposed to air. Aluminum is nontoxic in its metallic form, is not magnetic, and does not spark. Aluminum is ductile and malleable, which means it can be pulled into thin wires and is easy to hammer into thin sheets. Some gemstones are made from the crystal form of aluminum oxide known as corundum. Traces of other metals create various colors: sapphires get their blue color from cobalt and rubies get their red color from chromium. Artificial sapphires and rubies are easy and cheap to manufacture. Topaz is aluminum silicate colored yellow by traces of iron.
Chemical Properties
Alloys can be formed between aluminum and copper, zinc, magnesium, manganese and silicon. Although aluminum is active chemically, it does not corrode in moist air the way iron does. Instead, it quickly forms a thin, hard coating of aluminum oxide which sticks to the metal and protects it from further oxidation. Aluminum is part of a chemical compound that is also comprised of potassium, aluminum, sulfur and oxygen. Aluminum is an active metal that reacts with both hot acids and alkalies which is unusual for an element. Aluminum also reacts quickly with hot water. In powdered form, it catches fire quickly when exposed to a flame.
General Properties
Aluminum contains only one naturally occurring isotope, aluminum-27, and six radioactive isotopes. A radioactive isotope gives off either energy or subatomic particles. Radioactive aluminum isotopes have no commercial use. Aluminum is the metallic chemical element of atomic number 13 on the periodic table. The chemical symbol for aluminum is Al. The atomic weight of aluminum is 26.98, its specific gravity is 2.70, its melting point is 1,220.5 degrees F (660 degrees C), and its boiling point is 4,566.2 degrees F, or 2,519 degrees C.