Here's how to break down the formula:

* Mg: Magnesium is a group 2 element, so it has a +2 charge.

* H: Hydrogen has a +1 charge.

* TeO₄: Tellurate is the polyatomic anion derived from telluric acid (H₂TeO₄). It has a -2 charge.

To balance the charges, you need one magnesium ion (Mg²⁺), one hydrogen ion (H⁺), and one tellurate ion (TeO₄^2-).