Question

Why is the chemical formula for magnesium chloride `"MgCl"_2"`?

Answer 1

Refer to the explanation.

Explanation:

The Mg atom has two valence electrons and the Cl atom has seven valence electrons.

If the Mg atom loses its two valence electrons, it will become stable because the next lower energy level will have eight valence electrons (an octet). If a Cl atom gains one electron, it will have eight valence electrons.

Since Mg needs to lose two valence electrons, it is required that two Cl atoms each gain one Mg valence electron. The Mg atom becomes a `"Mg"^(2+)"` ion and each Cl atom becomes a `"Cl"^(-)"` ion. The ionic bond is the electrostatic attraction between oppositely charged ions.