How do you cross - valance compounds???

Question

I am trying to help my husband with his Hazmat Chemistry. Can you please explain to me how to cross-valence compounds to determine their formula? Thanks in advance!!!

Answer 1

I can only guess that you mean that if you have Al(3+) and O(2-), then you multiply the Al(3+) by 2 and the O(2-) by 3 to get Al2O3 for the compound between them.