Here's why:

* Calcium (Ca) is a metal and tends to lose two electrons to form a positively charged ion (Ca²⁺).

* Chlorine (Cl) is a non-metal and tends to gain one electron to form a negatively charged ion (Cl⁻).

* Ionic compounds are formed by the electrostatic attraction between oppositely charged ions. In CaCl₂, the two positive charges on the calcium ion are balanced by the two negative charges on the two chloride ions.