how to make ionic bond between aluminium and oxygen.explain

Dear Student

The valency of Al is 3 whereas the valency of oxygen is 2. Hence the formula of compound formed by the reaction of Al and oxygen is Al₂O₃. 
 

A balanced chemical equation showing the reaction of aluminium and oxygen is as follows

4Al + 3O₂ → 2Al₂O₃

The aluminium ion is present in +3 state and oxygen ion is present in -2 state.
Thus, to balance charges we require 2 Al^3 + ions and 3 O^2 - ions which gives total of -6 and +6.
Each aluminium atom donates 3 electrons out of which 2 electrons are accepted by one oxygen atom and 1 electron is accepted by other oxygen atom.
See the sharing of bonds between the atoms below in the picture:


Hope it is clear.

Regards