## Chemistry 9th Edition

Iron has two variable valencies - $Fe^{2+}$ and $Fe^{3+}$ But, on the other hand, Barium has no variable valency. So, when we write compounds of Iron, we specify which valency we are using, to avoid any confusion. e.g. Iron Oxide can mean - FeO (Ferrous Oxide) and $Fe_{2}O_{3}$ (Ferric Oxide)