Complete the following balanced equation: 4Al + 3O2 → ?

The correct answer is Option (2) → 2Al₂O₃

Aluminium has valency 3 and oxygen valency 2, so aluminium oxide is Al₂O₃. A balanced equation has the same number of atoms of each element on both sides.

• Left side: 4 Al atoms and \(3\times2=6\) O atoms

• Each Al₂O₃ has 2 Al and 3 O, so 4 Al and 6 O need 2Al₂O₃

• Right side: \(2\times2=4\) Al atoms and \(2\times3=6\) O atoms, matching the left side