and the salt magnesium sulfate. The symbol for magnesium is Mg, and sulfuric acid is a compound containing sulfur, oxygen, and hydrogen. Its formula is written: H2SO4. So we write Mg plus H2SO4.

For example, magnesium oxide is made up of two elements, magnesium and oxygen. Its formula is MgO. This shows that it has one atom of magnesium for every one atom of oxygen.