* Identify the ions:

* Barium (Ba) forms a +2 ion (Ba²⁺).

* Phosphate (PO₄) forms a -3 ion (PO₄³⁻).

* Balance the charges: To achieve a neutral compound, you need to find the least common multiple of the charges. In this case, the least common multiple of 2 and 3 is 6.

* Determine the subscripts:

* To get a +6 charge, you need 3 barium ions (3 Ba²⁺ = +6).

* To get a -6 charge, you need 2 phosphate ions (2 PO₄³⁻ = -6).

* Write the formula: The ionic formula for barium phosphate is Ba₃(PO₄)₂.