Answer the following
Why the ground-state electronic configurations of gadolinium and lutetium are different than expected?
Gadolinium and lutetium show different ground-state electronic configurations because the 5d and 4f-orbitals are near to the same energy due to which the next electron goes in 5d-orbital instead of 4forbital. This retains the extra stability achieved when the 4f orbital is half-filled and completely filled respectively. Thus, 5d orbital contains one electron in the case of gadolinium and lutetium.