Final answer:
In a chemical formula, the number of atoms of an element is indicated by the subscript number after the element symbol. For instance, aluminum sulfate has 2 aluminum atoms per formula unit, as denoted by Al2(SO4)3.
Step-by-step explanation:
The question "How many atoms of aluminum are there in one formula unit?" relates to the subject of Chemistry, specifically to the composition of chemical compounds. When we mention one formula unit, we're typically referring to the smallest whole number ratio of ions or atoms in an ionic compound. For instance, considering aluminum sulfate, Al2(SO4)3, each formula unit contains 2 aluminum atoms. This can be generally confirmed by looking at the chemical formula of a compound, where the subscript number after the element symbol (if present) indicates the number of atoms of that element in one formula unit. In the absence of a subscript, such as in Al2O3 for aluminum oxide, the number of aluminum atoms per formula unit is 2, as indicated by the subscript.