Aluminium shows a uniform oxidation of \(+3\). Like Aluminium, Tl also shows \(+3\) oxidation state in some of its compounds like \(\mathrm{TlCl}_3, \mathrm{Tl}_2 \mathrm{O}_3\), etc. Like \(\mathrm{Al}, \mathrm{Tl}\) also forms octahedral complexes: \(\left[\mathrm{AlF}_6\right]^{3-}\) and \(\left[\mathrm{TlF}_6\right]^3\). Group 1 metals shows \(+1\) oxidation state. Tl also shows \(+1\) oxidation state due to inert pair effect. Thus it resembles with group 1 metals.