Question

Modern definition say that a valency of element is twice the number of oxygen atoms present in oxygen reaction with the element but if we consider the compound Aluminium oxide,Al2O3 then how can we considere it twice of the oxygen atom is the valency of aluminium because the valency of Aluminium is not 6 but it is half of it, so please explain me how to find out the valency of aluminium in this case

Answer 1

here u can see that its Al2O3 means Al has 2 and O has 3 so by cris cross method u can get the answer just cross them and u will get Al has 3 as its valency and O has 2 as its valency which are their actual