Although most neutral d- and f-block atoms have nd(g-2)(n + 1)s(2) 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.

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The extraction of La, Eu, Lu, Y, Am and Cf by Adogen-464SCN from ammonium thiocyanate solutions has been studied as a Function of extractant and thiocyanate concentration. It has been shown that the degree of complex formation in the aqueous phase decreases across the lanthanide series and increases between Am and Cf. whereas in the organic phase it increases for both series. With respect to complexation in the aqueous phase, Y is midway between Eu and Lu, Am is near to La, and Cf is a pseudolanthanide lighter than La. On the other hand, it has been shown that with respect to complexation in the organic phase Am and Cf are out of the heavy end of the lanthanide series, and Y is near to La. Because the organic term prevails, the distribution ratio increases in the order La < Y < Eu < Lu < Am < Cf, except for very high concentrations of thiocyanate ions, where Am and Cf are less extracted than Lu.

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