Here's how to determine the number of valence electrons in the HPO₄⁻² ion:

1. Valence Electrons of Individual Atoms

* Hydrogen (H): 1 valence electron

* Phosphorus (P): 5 valence electrons

* Oxygen (O): 6 valence electrons

2. Total Valence Electrons

* H: 1

* P: 5

* O (x4): 6 x 4 = 24

* Charge (-2): Add 2 electrons (negative charge means gaining electrons)

3. Calculation

1 + 5 + 24 + 2 = 32 valence electrons

Therefore, the HPO₄⁻² ion has 32 valence electrons.