* Parentheses: The parentheses indicate that the subscript outside the parentheses applies to everything inside. So, we have three sulfate (SO₄) units.
* Subscripts: Each sulfate unit has four oxygen atoms (indicated by the subscript 4).
* Total: Since there are three sulfate units, we multiply: 3 units * 4 oxygen atoms/unit = 12 oxygen atoms.
Therefore, there are 12 oxygen atoms in the formula Al₂(SO₄)₃.
