Final answer:
The formula for calcium bromide is CaBr₂ because the 2+ charge of calcium is neutralized by two 1- bromide ions.
Step-by-step explanation:
The correct formula for calcium bromide, which has two bromide ions for each calcium ion, is CaBr₂. This is because calcium typically has a 2+ charge (Ca²⁺), while a bromide ion carries a 1- charge (Br⁻). To achieve electrical neutrality, two bromide ions are required to balance the charge of one calcium ion, resulting in the formula unit CaBr₂. The proper notation of an ionic compound's formula ensures that the charges balance out and the compound is electrically neutral, as demonstrated in the examples provided in the referenced material.