Here's why:

* Calcium (Ca) is a metal that forms a +2 cation (Ca²⁺) when it loses two electrons.

* Chloride (Cl) is a nonmetal that forms a -1 anion (Cl⁻) when it gains one electron.

* To form a neutral compound, the charges must balance. Since calcium has a +2 charge and chloride has a -1 charge, you need two chloride ions to balance one calcium ion.

Therefore, the chemical formula for calcium chloride is CaCl₂.