* Calcium (Ca) is a metal in Group 2 of the periodic table, meaning it has 2 valence electrons (electrons in its outermost shell).
* Chlorine (Cl) is a nonmetal in Group 17, meaning it has 7 valence electrons and wants to gain one more to complete its octet.
To achieve stability, calcium will lose its 2 valence electrons, becoming a +2 cation (Ca²⁺). Each chlorine atom will gain one electron, becoming a -1 anion (Cl⁻). To balance out the charges, you need two chlorine atoms to accept the two electrons from one calcium atom:
* Ca²⁺ + 2Cl⁻ → CaCl₂
This forms the compound calcium chloride (CaCl₂).
