There are two steps in the extraction of copper metal from chalcocite, a copper ore. in the first step, copper (i) sulfide and oxygen react to form copper (i) oxide and sulfur dioxide: (s) (g) (s) (g) in the second step, copper (i) oxide and carbon react to form copper and carbon monoxide:

Balanced chemical reaction 1:

2Cu₂S (s) + 3O₂ (g) → 2Cu₂O (s) + 2SO₂ (g).

Balanced chemical reaction 2:

Cu₂O (s) + C (s) → 2Cu (s) + CO (g). / ·2

2Cu₂O (s) + 2C (s) → 4Cu (s) + 2CO (g)

Balanced net chemical equation:

2Cu₂S (s) + 3O₂ (g) + 2C (s) → 4Cu (s) + 2CO (g) + 2SO₂ (g).

There 4 atoms of copper, 6 oxygens, 2 sulfur and 2 carbons on both side of reaction.