Aluminium (Al) generally exhibits + 3 oxidation state in its compounds. Thallium (Tl), the last member of the group 13, shows oxidation state of +3 i.e., $Tl_2O_3$. Like Al, Tl form octahedral complexes i.e., $[TlF_6]^{3–}$. Tl like alkali metals shows oxidation state of +1 (due to inert paireffect). TlOH like NaOH is soluble in water and the solution is stronglyalkaline. Like alkali metals, $Tl_2SO_4$ forms a double sulphate with $Al_2(SO_4)_3$which is soluble in water.