I know that to aid the symmetry of singly occupied orbitals one electron jumps from 4s orbital to 3d orbital thus giving Chromium the configuration 3d5 4s1.
But my question is, when we're evaluating the quantum numbers of the last electron, shouldn't we definitively use the farthest electron from the nucleus? Irrespective of which electron is assorted last. Because it's not like a Chromium atom is created by sequentially inserting electrons one after the other voluntarily.
In a perfectly stable Chromium atom, which has the configuration Ar(18) 3d5 4s1, the last or ultimate electron in terms of energy level, orbital and radius, should be the 4s1 electron. Why is it that most references I found tell me to consider the 3d5 electron?