The formula for the compound formed by lead ions (Pb²⁺) and chromate ions (CrO₄²⁻) is PbCrO₄.

Here's how we arrive at this:

* Lead ions have a +2 charge (Pb²⁺).

* Chromate ions have a -2 charge (CrO₄²⁻).

Since the charges are equal and opposite, they balance each other out in a 1:1 ratio, resulting in the formula PbCrO₄.