Why the formula of magnesium chloride is MgCl2?

Answer 1

Magnesium chloride is an neutral ionic compound. In neutral ionic compounds, the positive charge of the cations must balance out the negative charge of the anions.

In the case of magnesium chloride, magnesium is the cation with an ionic charge of +2 and chlorine is the anion with an ionic charge (each) of -1.

Since two chlorine anions together have a charge of -2 total, they balance out the one magnesium cation with a charge of +2.

Answer 2

Magnesium chloride has a chemical formula of MgCl2 because magnesium has a +2 charge while chloride has a -1 charge. To balance the charges and achieve a neutral compound, two chloride ions are needed for every one magnesium ion, resulting in the formula MgCl2.