You're asking about the number of atoms in a formula unit of aluminum oxide. Here's how to figure that out:

* The formula for aluminum oxide is Al₂O₃.

* This formula tells us there are 2 aluminum (Al) atoms and 3 oxygen (O) atoms in each formula unit.

* Total atoms: 2 (Al) + 3 (O) = 5 atoms

Therefore, there are 5 atoms in a formula unit of aluminum oxide.