# How can I name ionic compounds with transition metals?

May 31, 2014

Same way as you would any other ionic compound, but with the addition of a notation in Roman numerals after the transition metal name to show what it's oxidation number is. This is needed because transition metals have variable oxidation numbers and so there would otherwise be more more than one different compound with the same name and that would be ambiguous.

For example, we can make compounds of iron and chlorine which would be named iron chloride. Iron can have an oxidation number of +2 or +3 and hence we could make $F e C {l}_{2}$ or $F e C {l}_{3}$. To be able to tell these apart, we call the first one iron(II) chloride and the second one iron(III) chloride.