1. Determine the charges of the ions:
* Calcium (Ca) is in group 2 of the periodic table, so it forms a +2 ion (Ca²⁺).
* Sulfur (S) is in group 16 (or VIA), so it forms a -2 ion (S²⁻).
2. Balance the charges:
* Since the charges have the same magnitude but opposite signs, they already balance perfectly.
3. Write the formula:
* The formula for the ionic compound is simply CaS.
Therefore, the ionic compound formula between calcium and sulfur is CaS.
