If every oxygen ion (combined with an aluminum ion) has a charge of –2, what must the charge of each aluminum ion be? How can you tell this? Also, what has to happen to an uncharged aluminum atom so that it will bond with oxygen?

Question

anonymous · Answer

@shrutipande9

aaronq · Answer

An aluminium ion has a charge of +3, this is because of it's electronic configuration; it loses it's $3s^2$ and $ 3p^1$ electrons to gain stability - in other words, it is $\sf oxidized$.

Since the compound is neutral, the stoichiometry needs to be $Al_2O_3$.