Systematic Names

The names of compounds include the oxidation state of the element that can have variable oxidation states in Roman numerals.For example, in iron(II) sulfate and iron(III) chloride, the iron has oxidation states of +2 and +3 respectively.This tells you that they contain Fe²⁺ and Fe³⁺ ions.This can also be extended to negative ions.Iron(II) sulfate is FeSO₄. The compound FeSO₃ had the old name of iron(II) sulfite.The modern names reflect the oxidation states of the sulfur in the two compounds. The sulfate ion is SO₄^2- and is called the sulfate(VI) ion with the sulfur in the oxidation state of +6.The sulfite ion is SO₃^2-. The oxidation state of the sulfur is +4 and this is called the sulfate(IV) ion.The ate ending simply shows that the sulfur combines with oxygen to form a negative ion.