* Calcium (Ca): Calcium is a metal in Group 2 of the periodic table. Metals tend to lose electrons to form positively charged ions called cations. Calcium loses two electrons to achieve a stable electron configuration, forming a Ca²⁺ cation.

* Bromine (Br): Bromine is a nonmetal in Group 17 of the periodic table. Nonmetals tend to gain electrons to form negatively charged ions called anions. Bromine gains one electron to achieve a stable electron configuration, forming a Br⁻ anion.

In calcium bromide:

* The calcium ion (Ca²⁺) has a +2 charge.

* Each bromide ion (Br⁻) has a -1 charge.

To balance the charges, you need two bromide ions for every one calcium ion. This gives a total of +2 from the calcium and -2 from the two bromides, resulting in a neutral compound.

Therefore, the ionic formula for calcium bromide is CaBr₂.