On moving down in a group, the atomic radius of the atomic radius increases generally. Similarly, the atomic radius of Indium is higher than that of Aluminium. read more
Indium and Aluminium come in the same group. And as we know that the ionization energy decreases down the group and Indium comes below Al, therefore, the ionization energy of Indium is lower than Al. Ionization energy is the energy used to remove an electron from the outermost shell of the atom. read more