Will give medal! what is the reason the group 13 metals have a typical charge of 3+?

My

13 group of the periodic table represented by boron, aluminum and gallium subgroup. It includes gallium, indium, thallium. Typical steper oxidation in the subset gallium 3 is explained by the presence of (n-1)d^10 E-configuration.
Aluminium oxidation degree has +3 an electronic configuration of noble gases S^2P^6

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