The sublevels of each principal level are not degenerate for multielectron atoms.
B
In a hydrogen atom, the sublevels of each principal level are degenerate.
C
Due to shielding, the 3d orbitals lie lower in energy than the 4s orbital.
D
Some atoms have anomalies in their electron configurations due to the fact that energy separations of the orbitals become smaller as the principal quantum number increases.
