Here's how to determine the number of oxygen atoms in molybdenum(III) phosphate:

1. Determine the Chemical Formula:

* Molybdenum(III): This indicates the molybdenum ion has a +3 charge (Mo³⁺).

* Phosphate: The phosphate ion is PO₄³⁻.

To balance the charges, we need one Mo³⁺ ion and one PO₄³⁻ ion. Therefore, the chemical formula is MoPO₄.

2. Count the Oxygen Atoms:

The formula MoPO₄ shows that there are four oxygen atoms in one molecule of molybdenum(III) phosphate.