How will the Fe reach noble gas configuration? The problem I have is that, for example in FeO, iron may keep its 8 valence electrons, but it still won't reach noble gas configuration nor electron octet.
Iron has the electron configuration:
When it forms FeO the 2 outer 4s electrons are lost to form
Iron has 8 valence electrons and its most common oxidation states are +2 and +3. In non of these does it attain a noble gas configuration.
This is because is because the octet "rule" is a rule and not a law so is not applicable in all cases. In fact it only applies to a limited number of elements.