The formula of the compound formed between barium (Ba) and chlorine (Cl) is BaCl₂. Here's why:

* Barium is in group 2 of the periodic table, making it an alkaline earth metal. It has a +2 charge when it forms ions.

* Chlorine is in group 17 (halogens), and it has a -1 charge when it forms ions.

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