Can we begin at the beginning When chemists put a standard electron configuration for an element what do those numbers represent Do they mean to suggest that each of those pairs of electrons occupies a mere Slatter determinant That they sit in things that are no more real than a basis function like the cartesian axes are basis functions for vectors And any old set of basis functions could be used instead Or do these electrons reside in pairs in Hartree Fock orbitals which now just so happen to be called 3d something or other as though they WERE a hydrogenic atomic orbitals even though they aren t What DO those numbers mean in an atom s electron configuration notation Do they now mean the first two quantum numbers of the one electron Hartree Fock wavefuctions and we re now highjacked Schroediger hydrogenic notation for them but forgot to tell anybody Inquiring minds want to know