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The Element Aluminum

Veröffentlicht: 2014-06-28    Klicken: 14     Quelle: Jefferson Lab

Atomic Number: 13

Atomic Weight: 26.9815386

Melting Point: 933.437 K (660.323°C or 1220.581°F)

Boiling Point: 2792 K (2519°C or 4566°F)

Density: 2.70 grams per cubic centimeter

Phase at Room Temperature: Solid

Element Classification: Metal

Period Number: 3    Group Number: 13    Group Name: none

What's in a name? From the Latin word for alum, alumen.

Say what? Aluminum is pronounced as ah-LOO-men-em.

History and Uses:

Although aluminum is the most abundant metal in the earth's crust, it is never found free in nature. All of the earth's aluminum has combined with other elements to form compounds. Two of the most common compounds are alum, such as potassium aluminum sulfate (KAl(SO4)2·12H2O), and aluminum oxide (Al2O3). About 8.2% of the earth's crust is composed of aluminum.

Scientists suspected than an unknown metal existed in alum as early as 1787, but they did not have a way to extract it until 1825. Hans Christian Oersted, a Danish chemist, was the first to produce tiny amounts of aluminum. Two years later, Friedrich Wöhler, a German chemist, developed a different way to obtain aluminum. By 1845, he was able to produce samples large enough to determine some of aluminum's basic properties. Wöhler's method was improved in 1854 by Henri Étienne Sainte-Claire Deville, a French chemist. Deville's process allowed for the commercial production of aluminum. As a result, the price of aluminum dropped from around $1200 per kilogram in 1852 to around $40 per kilogram in 1859. Unfortunately, aluminum remained too expensive to be widely used.

Two important developments in the 1880s greatly increased the availability of aluminum. The first was the invention of a new process for obtaining aluminum from aluminum oxide. Charles Martin Hall, an American chemist, and Paul L. T. Héroult, a French chemist, each invented this process independently in 1886. The second was the invention of a new process that could cheaply obtain aluminum oxide from bauxite. Bauxite is an ore that contains a large amount of aluminum hydroxide (Al2O3·3H2O), along with other compounds. Karl Joseph Bayer, an Austrian chemist, developed this process in 1888. The Hall-Héroult and Bayer processes are still used today to produce nearly all of the world's aluminum.

With an easy way to extract aluminum from aluminum oxide and an easy way to extract large amounts of aluminum oxide from bauxite, the era of inexpensive aluminum had begun. In 1888, Hall formed the Pittsburgh Reduction Company, which is now known as the Aluminum Company of America, or Alcoa. When it opened, his company could produce about 25 kilograms of aluminum a day. By 1909, his company was producing about 41,000 kilograms of aluminum a day. As a result of this huge increase of supply, the price of aluminum fell rapidly to about $0.60 per kilogram.

Today, aluminum and aluminum alloys are used in a wide variety of products: cans, foils and kitchen utensils, as well as parts of airplanes, rockets and other items that require a strong, light material. Although it doesn't conduct electricity as well as copper, it is used in electrical transmission lines because of its light weight. It can be deposited on the surface of glass to make mirrors, where a thin layer of aluminum oxide quickly forms that acts as a protective coating. Aluminum oxide is also used to make synthetic rubies and sapphires for lasers.

Estimated Crustal Abundance: 8.23×104 milligrams per kilogram

Estimated Oceanic Abundance: 2×10-3 milligrams per liter

Number of Stable Isotopes: 1   (View all isotope data)

Ionization Energy: 5.986 eV

Oxidation States: +3


2s2   2p6

3s2   3p1