* Ionic compounds are formed by the electrostatic attraction between positively charged ions (cations) and negatively charged ions (anions).

* Sodium (Na) is a metal and forms a +1 cation (Na+).

* Aluminum (Al) is a metal and forms a +3 cation (Al3+).

* Phosphate (PO4) is a polyatomic ion with a -3 charge.

In sodium aluminum phosphate, the sodium and aluminum cations bond with the phosphate anion through electrostatic forces, creating an ionic compound.