Although most neutral d- and f-block atoms have nd g  2(n+1)s2 and (n- 1)f g  -  2 (n+ 1)s 2  ground configurations, respectively, where g is the group number (i.e., number of valence electrons), one-third of these 63 atoms prefer a higher d-population, namely via (n+1)s→nd "outer" to "inner" electron shift (particularly atoms from the second d-row), or via (n-1)f→nd "inner" to "outer" electron shift (particularly atoms from the second f-row). Although the response to the modified self-consistent field is orbital destabilization and expansion for (n+1)s→nd, and stabilization and contraction for (n-1)f→nd, the relativistic modification of the valence orbital responses is stabilization in both cases. This is explained by double perturbation theory. Accordingly, electron configuration and relativity trigger the orbital energies, the orbital populations and the chemical shell effects in different ways. The particularly pronounced relativistic effects in groups 10 and 11, the so-called gold maximum, occur because of particularly efficient cooperative nonrelativistic shell effects and relativistic stabilization effects (inverse indirect effect) at the end of the d-block.
['Jochen Autschbach', 'S. Siekierski', 'Michael Seth', 'Peter Schwerdtfeger', 'W. H. E. Schwarz']
Dependence of relativistic effects on electronic configuration in the neutral atoms of d- and f-block elements