* Barium (Ba) is in Group 2 of the periodic table, meaning it has a +2 charge when it forms an ion (Ba²⁺).

* Bromine (Br) is in Group 17, meaning it has a -1 charge when it forms an ion (Br⁻).

To balance the charges and create a neutral compound, you need two bromide ions (2 x -1 = -2) to cancel out the +2 charge of the barium ion.

Therefore, two bromide ions (Br⁻) can combine with one barium ion (Ba²⁺) to form barium bromide (BaBr₂).