Here's how to determine the number of valence electrons in the phosphate ion (PO₄³⁻):

1. Valence Electrons of Individual Atoms

* Phosphorus (P): Group 15, so it has 5 valence electrons.

* Oxygen (O): Group 16, so it has 6 valence electrons.

2. Total Valence Electrons for the Ion

* Phosphorus: 5 valence electrons

* Oxygen (4 atoms): 6 valence electrons/atom * 4 atoms = 24 valence electrons

* Charge: The 3- negative charge indicates the ion has gained 3 extra electrons.

3. Total Valence Electrons

5 + 24 + 3 = 32 valence electrons

Therefore, the phosphate ion (PO₄³⁻) has 32 valence electrons.