I've read that in the 13th period, Ga has higher I.E. than Al because of the filling of the d-orbitals in Ga.
The text said they have low penetration,hence they don't shield well and the effective nuclear charge on the valence electrons increases.
But, shouldn't Germanium have a higher I.E. than Silicon by the same logic? Why doesn't it?
Also, why does Indium again have lower I.E. even though it has filled d-orbitals.