Aluminium is usually found in +3 oxidation stagte. In contarast, thallium exists in +1 and +3 oxidation states. This is due to :
(1) lanthanoid contraction
(2) lattice effect
(3) diagonal relationship
(4) inert pair effect
(1) lanthanoid contraction
(2) lattice effect
(3) diagonal relationship
(4) inert pair effect