The formula for sodium phosphate is Na₃PO₄, not Na₄PO₄.

Here's why:

* Sodium (Na) has a +1 charge.

* Phosphate (PO₄) has a -3 charge.

To balance the charges and create a neutral compound, you need three sodium ions (+3) to combine with one phosphate ion (-3). This results in the formula Na₃PO₄.