Metal Oxide - GCSE Chemistry Definition

A metal oxide is a compound formed when a metal reacts with oxygen. It contains metal ions and oxide ions (O^2-). Most metal oxides are solids at room temperature and often occur as minerals in nature.

For example, when iron reacts with oxygen, it forms iron(III) oxide (Fe₂O₃), commonly known as rust.

Many metal oxides act as bases and can react with acids to form a salt and water in neutralisation reactions:

metal oxide + acid → salt + water

Metal oxides have various applications, such as in building materials (e.g. cement and ceramics) and electronics (e.g. semiconductors). Understanding metal oxides is important in GCSE Chemistry for explaining oxidation, metal reactivity, and acid–base reactions.