posted by candy
A textbook says that each ion in an ionic compound has the noble gas configuration. What about aluminium oxide?
Al has lost its three outside electrons, oxygen has gained two electrons. Now the outside shell of Al has 8 (it was 2,8,3) and oxygen has 8 (it was 2,6). The Al now has a +3 charge (having lost 3 electrons) and the oxygen has a charge of -2 since it gained two electrons.