Here's why:
* Copper(I) means the copper ion has a +1 charge (Cu⁺).
* Phosphate is the polyatomic ion PO₄³⁻ with a -3 charge.
To balance the charges, we need three copper ions (3 x +1 = +3) to match the -3 charge of the phosphate ion. This gives us the formula Cu₃PO₄.
