Here's how to figure that out:

* Cesium is a Group 1 element (alkali metal), and its symbol is Cs. It forms a +1 cation (Cs⁺).

* Sulfate is a polyatomic ion with the formula SO₄²⁻.

To balance the charges, you need two cesium ions (2 x +1 = +2) to combine with one sulfate ion (-2).