Aluminum is the chemical element with the symbol Al and is the most abundant metal in Earth’s crust.
Aluminum has atomic number 13 and is a lightweight, silvery metal. It is not usually found as a native metal because it bonds readily with oxygen and occurs mainly in minerals, especially those in bauxite ores. Industrial aluminum production uses the Bayer process to make alumina and the Hall–Héroult process to reduce alumina to metal by electrolysis.
A thin oxide layer forms quickly on exposed aluminum, helping protect the underlying metal from further corrosion. This combination of low density, strength in alloys, and corrosion resistance makes aluminum useful in aircraft, packaging, construction, transport, and electrical products.
The spelling differs between “aluminum” and “aluminium”; both refer to the same element. Aluminum is not the most abundant element in Earth’s crust overall—that distinction belongs to oxygen—but it is the most abundant metal there.