The correct formula unit for cesium bromide is made up of 1 Cs⁺ ion and 1 Br⁻ ion.
Cesium bromide (CsBr) is an ionic compound formed by the combination of cesium ions (Cs⁺) and bromide ions (Br⁻) in a 1:1 ratio. Therefore, the answer is:
1 Cs⁺ ion and 1 Br⁻ ion.