Final answer:
The formula of the compound, cesium bromide, which crystallizes with a cubic unit cell containing bromide ions at the corners and a cesium ion in the center, is CsBr, having a 1:1 cation:anion ratio.
Step-by-step explanation:
If cesium bromide crystallizes with a cubic unit cell that contains bromide ions at the corners and a cesium ion in the center, the formula of the compound can be determined based on the arrangement of ions within the unit cell. In a simple cubic unit cell structure, each corner atom is shared by eight surrounding unit cells. Therefore, with one bromide ion at each of the eight corners, there is effectively 1 bromide ion (since each corner ion is 1/8th inside the actual unit cell). With a single cesium ion in the center that is fully contained within the unit cell, the stoichiometry is a 1:1 ratio of cesium ions to bromide ions, giving us the formula CsBr.
Similar to the cesium chloride structure, cesium bromide also forms a type of structure with large cations and having a 1:1 cation: anion ratio. The description analogous to cesium chloride, in terms of coordination number and structure, helps in predicting the formula of cesium bromide as well.