Here's how to determine the oxidation state of phosphorus in PO₃³⁻:

1. Assign Oxidation States to Oxygen

* Oxygen typically has an oxidation state of -2, unless it's in a peroxide (where it's -1) or bonded to fluorine.

2. Determine the Overall Charge

* The phosphate ion (PO₃³⁻) has a charge of -3.

3. Set up an Equation

Let 'x' represent the oxidation state of phosphorus:

x + 3(-2) = -3

4. Solve for 'x'

x - 6 = -3

x = +3

Therefore, the oxidation state of an individual phosphorus atom in PO₃³⁻ is +3.