[lokifenrir96]

Say you have an element with 25 electrons, in which case the spdf electronic configuration would look like this:
1s2 2s2 2p6 3s2 3p6 3d5 4s2

I understand that when the orbitals are unfilled, the 4s subshell has lower energy than the 3d subshell. So the 4s subshell is filled first, then its energy level spikes to above that of the 3d subshell, then the 3d subshell is filled. Hence, if 4 electrons were removed from this element, 2 would first come from 4s subshell (which now has the highest energy level) then the next 2 from the 3d subshell.

But what if we have another element with 33 electrons?
1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p3

In this  case, after the 3d subshell is completely filled, does its energy level spike to above that of 4s or does it remain below that of 4s? This is important because if we were to remove 4 electrons from this element, the first 3 would come from 4p subshell (since it has the highest energy level), but the last electron could come from either 3d or 4s subshell depending on whether the 3d subshell's energy increased to above that of 4s after the 3d subshell was completely filled.

Thank you!