Metal

Metal is a class of chemical elements with characteristic properties: a shiny surface when polished, and the ability to conduct electricity and heat well. Most metals can be worked, bent, or drawn into wire or sheet without breaking. Common examples are iron, copper, aluminium, tin, gold, and silver.

Most elements in the periodic table are metals. There also exist elements called metalloids, which occupy a middle ground between metals and non-metals in their properties, such as silicon. The Somali word 'bir' sometimes refers specifically to iron, but the scientific meaning is broader.

Technical properties

The key properties of metals stem from how their atoms are bonded: electrons in the outer shells move freely through the structure, enabling the conduction of electricity and heat. This same arrangement allows metals to be worked and drawn into wire or sheet without cracking, unlike ceramics.

Extraction and processing

Most metals do not occur in pure form in nature, but exist in ore containing other elements such as oxygen or sulfur. Extraction requires mining and then refining, usually carried out in high-temperature furnaces or by electrolysis. Aluminium, for example, is extracted from bauxite ore using large amounts of electricity.

Alloys and corrosion

Metals are often used not in pure form but as alloys, in which two or more elements are combined. Steel is iron with added carbon; bronze is copper and tin. Alloys are generally stronger than pure metal. On the other hand, many metals naturally react with oxygen and water, causing corrosion or oxide film on the surface.

Uses and economy

Metal is fundamental to industry: construction, vehicles, electrical wiring, electronics, and medical equipment all depend on it. Metal can also be recycled, which requires less energy than new extraction. Some metals, such as gold and silver, have long held value as currency and stores of wealth.