Iron (II) oxide’s Lewis Structure is among one of the easiest to draw. The iron atom, because it has a +2 charge in this compound, is drawn with two valence electrons – and since it is a metal, it wants to give them away (“lose them”).
Oxygen, by contrast, is a non-metal with six valence electrons – that’s just two short of a full valence shell. The high electronegativity of oxygen attracts the electrons that iron wants to give away, and the two bond together.
“Bond together” in this case means making an ionic compound. There are no MOLECULES of iron (II) oxide – instead there is a crystal lattice of alternating positive and negative ions.
The iron atoms, which each lost two electrons, have a +2 charge and become cations. The oxygen atoms, which each gained two electrons, have a -2 charge and become anions.
This ionic compound has the same number of cations and anions in the crystal, since they occur in a 1:1 ratio.