* Barium (Ba) is in group 2 of the periodic table, meaning it has a +2 charge as a cation (Ba²⁺).
* Sulfur (S) is in group 16 of the periodic table, meaning it has a -2 charge as an anion (S²⁻).
To form a neutral compound, the charges must balance. Since barium has a +2 charge and sulfur has a -2 charge, one atom of each element is needed. This results in the formula BaS.
