If Aluminum has 13 electrons, 3 of which are valence electrons and Oxygen has 8 electrons, 6 of which are Valence electrons.Aluminum gives 2 to Oxygen and so Oxygen has a 2- charge, right? and Aluminum has a 2+ charge right? I am confused by what this has to do with Ionic formula which requires 2 aluminum atoms and 3 oxygen atoms to join and have a 0 net chargePlease explain.You\'re very close: Why does Al only donate 2 electrons? Aluminum donates 3 electrons meaning it has a +3 charge: You noted that aluminum has 3 valence electrons, oxygen has 6: Valence electrons are the outermost electrons, and each element wants 8 valence electrons, hence the octet rule Oxygen has 6, if it gains 2 more electrons it will have 8Aluminum has 3, if it loses all 3 it will have 8 valence electrons a similar structure to [Ne] (the noble gas) Aluminum donates three electrons and oxygen accepts 2 Aluminum donates three electrons making it Al 3+ , oxygen has a charge of 2- Every 2 aluminum needs three oxygen molecules hence: Al2O3Other related question