I am writing out ionic compounds. The compound given is Fe(subscript)2O(subscript)3. I noticed on the periodic table iron had a charge of 3+/2+. Which should I then write down in the cation column of my ionic compound chart? Thank you.

Question

I am writing out ionic compounds.  The compound given is Fe(subscript)2O(subscript)3.  I noticed on the periodic table iron had a charge of 3+/2+.  Which should I then write down in the cation column of my ionic compound chart? Thank you.

DrBob222 · Answer

You must figure it out.
All compounds are neutral.
Fe2O3 (you are correct that Fe can have oxidation states or valences of +2 as well as +3). So you look at oxygen. It is -2, -2*3 = -6; therefore, Fe must be +6 and since there are two of them each must be +6/2 = +3.
A compound like FeO has Fe of +2.
Then for the fun of it look at Fe3O4. Funny business going on there.