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.

Bis the