The formula of platinum(IV) oxide is PtO₂. Here's how to figure that out:

* Platinum(IV) tells us that the platinum ion has a +4 charge (Pt⁴⁺).

* Oxide refers to the oxygen ion, which has a -2 charge (O²⁻).

To balance the charges, we need two oxygen ions for every platinum ion:

* Pt⁴⁺ + 2 O²⁻ → PtO₂