Most metals are found in the Earth as metal oxides. To extract the pure metal, the oxygen must be removed. The method used depends on the metal’s reactivity.

What is a metal oxide?

• A metal oxide is a compound of a metal and oxygen
• These form when metals react with oxygen in the environment
• To extract the metal, we must remove the oxygen – this is called reduction

Reduction with carbon

Metals less reactive than carbon can be extracted from their oxides by reduction with carbon.

• Carbon displaces the oxygen from the metal oxide
• The metal is left behind as a pure element

Example:
Iron(III) oxide + carbon → iron + carbon dioxide
2Fe₂O₃ + 3C → 4Fe + 3CO₂

💡 This is used in a blast furnace to extract iron.

Electrolysis of metal oxides

Metals more reactive than carbon (e.g. aluminium) are extracted from metal oxides using electrolysis.

• The metal oxide is melted and electricity is passed through
• The metal forms at the negative electrode
• This process is expensive because it requires a lot of energy

Example:
Aluminium oxide → aluminium + oxygen (using electricity)

Unreactive metals

Unreactive metals (like gold and silver) do not form oxides easily
They are often found as pure metals in the Earth and do not need reduction.

Why use carbon or electricity?

💡 Carbon acts as the reducing agent – it removes oxygen from the metal oxide.