Aluminum 101

Are Two I's Better Than One?
In the United States, we call it "aluminum." But the rest of the world, including the International Union of Pure and Applied Chemistry, calls it "aluminium." You can trace the confusion back to Sir Humphry Davy, who first identified the then-unknown element as "alumium." This he later changed to "aluminum" and finally to "aluminium," which carried an ending similar to potassium and sodium, other metals Davy discovered.

Like dozens of other elements on the periodic table, aluminum is naturally occurring. As with all elements, aluminum is a pure chemical substance that can't be broken down into something simpler. All elements are arranged in the periodic table by their atomic number -- the number of protons in their nucleus. Aluminum's lucky number is 13, so an aluminum atom has 13 protons. It also has 13 electrons.

The elements located above and below aluminum on the periodic table form a family, or group, that shares similar properties. Aluminum belongs to group 13, which also includes boron (B), gallium (Ga), indium (In) and thallium (Tl). The table to the right shows how these elements would be arranged on the periodic table. Notice that each element is represented by a symbol and that the symbol for aluminum is Al. The number above each symbol is the element's atomic weight, measured in atomic mass units (amu). Atomic weight is the average mass of an element determined by considering the contribution of each natural isotope. Aluminum's atomic weight is 26.98 amu. The number below aluminum's symbol is its atomic number.

­­Group 13
The Boron Family

10.81

B

5

26.98

Al

13

69.72

Ga

31

114.82

In

4­9

204.38

Tl

8

Chemists classify the elements in group 13 as metals, except for boron, which isn't a full-fledged metal. Metals are generally shiny elements that conduct heat and electricity well. They're also malleable -- able to be hammered into various shapes -- and ductile -- able to be drawn into wires. These characteristics certainly apply to aluminum. In fact, aluminum is often used in cookware because it conducts heat so efficiently. And only copper conducts electricity better, which makes aluminum an ideal material for electrical material, including light bulbs, power lines and telephone wires. Other important properties of aluminum are listed below:

  • Melting point: 660 degrees C (933 K; 1,220 degrees F)
  • Boiling point: 2,519 degrees C (2,792 K; 4,566 degrees F)
  • Density: 2.7 g/cm3
  • High reflectivity
  • Nonmagnetic
  • Nonsparking
  • Resistant to corrosion

These final two properties make aluminum particularly useful. Its corrosion resistance is due to chemical reactions that take place between the metal and oxygen. When aluminum reacts with oxygen, a layer of aluminum oxide forms on the outside of the metal. This thin layer shields the underlying aluminum from the corrosive effects of oxygen, water and other chemicals. As a result, aluminum is especially valuable for use outdoors. It also doesn't produce sparks when struck, which means you can use it near flammable or explosive materials.

Aluminum exists in nature in various compounds. To take advantage of its properties, it must be separated from the other elements that combine with it -- a long, complex process that starts with a rock-hard material known as bauxite.

After it undergoes that process, aluminum is very soft and lightweight in its pure form. Sometimes it's desirable to change these properties -- to make aluminum stronger and harder, for instance. To accomplish this, metallurgists will combine aluminum with other metallic elements, forming what are known as alloys. Aluminum is commonly alloyed with copper, magnesium and manganese. Copper and magnesium increase the strength of aluminum, while manganese enhances aluminum's corrosion resistance.