What is the proper chemical name for MgSO4?

Magnesium sulfate is the correct chemical name for MgSO4. This compound consists of one magnesium ion (Mg²⁺) and one sulfate ion (SO4²⁻). The sulfate ion is a polyatomic ion that contains sulfur and oxygen, which is indicated by the "SO4" in the formula. The nomenclature follows the convention where the metal (magnesium) is named first, followed by the name of the polyatomic ion (sulfate).

The other options do not correspond to the chemical formula MgSO4. Magnesium chloride is composed of magnesium and chloride ions, magnesium phosphate contains magnesium and phosphate ions, and magnesium nitrate consists of magnesium and nitrate ions. Thus, only magnesium sulfate accurately reflects the composition of the compound represented by the formula MgSO4.