Here's how to determine this:

* Lead(IV) indicates that the lead ion has a +4 charge (Pb⁴⁺).

* Iodide refers to the iodide ion, which has a -1 charge (I⁻).

To balance the charges, you need four iodide ions (4 x -1 = -4) to neutralize the +4 charge of the lead ion. This results in the formula PbI₄.