Ionic compound. How does monatomic work? For instance iron can make Fe2+ and Fe3+ how and why? Please help

Question

Ionic compound/bond. How does monatomic work? For instance iron can make Fe2+ and Fe3+ how and why? Please help

 

Where does the 2 and 3 come from in Fe2/3+? Ive heard it is to balance the formula but how exactly do you do that? Please excuse my english, I am not a native english speaker. 

Answer 1

Iron, Fe, has [Ar] 3d6 4s2

In order for Fe to become Fe2+, it loses 2 electrons, and becomes [Ar] 3d6

In order for Fe to become Fe3+, it loses an additional electron, and becomes [Ar 3d5

 

It does balance the formula in the sense that the charge on the anion must match that on the iron, so, e.g. if you have Fe(II) oxide, it is FeO, but iron(III) oxide is Fe2O3.