Here's how to determine the formula for the compound formed by lead(II) and chromate ions:

* Lead(II) ion: Pb²⁺

* Chromate ion: CrO₄²⁻

Steps to write the formula:

1. Identify the charges: Lead(II) has a +2 charge, and chromate has a -2 charge.

2. Balance the charges: Since the charges are equal and opposite, the formula is simply PbCrO₄.

Therefore, the compound formed by lead(II) and chromate ions is lead(II) chromate, with the formula PbCrO₄.