Ground states lanthanides, actinides

Table 1. Ground state and first excited state configurations, and their energy difference, for lanthanides and actinides...

The energy level values of the lowest spectroscopic term of the electronic configuration of lanthanide as well as actinide atoms, were tabulated by Brewer. Such tables are very useful for phenomenological correlations concerning actinide metals (see Chap. C). From these tables one can obtain Table 1 giving the ground state and the first excited level of the actinide atoms as well as of the lanthanide atoms for comparison ... 

Table 5. Ground state properties of heavy actinide metals (from Am to Es), emphasizing the lanthanide-like character of this part of the series...

From Fig. 8, one notices that the localized enthalpy is lower by about 0.9 eV than the itinerant one, thus classifying americimn metal among the lanthanide-like, heavier actinides. The picture is consistent with the results of magnetic measurements, which explain magnetism in americium metal as derived from a 5f, J s 0 atomic ground state. 

Figure 1.16 The ground state electronic repnlsive stahilization energy 1 as a fnnction of the 4f electron nnmher q (the contribution from the F term in Eqnation 1.3, solid hne the contribntion from the term in Eqnation 1.3, dashed line) [15]. (Reprinted from Journal of Inorganic and Nuclear Chemistry, 32, L.J. Nngent, Theory of the tetrad effect in the lanthanide(lll) and actinide(lll) series, 3485-3491, 1970, with permission from Elsevier.)...

Using Fig. 12.29, list elements (ignore the lanthanides and actinides) that have ground-state electron configurations that differ from those we would expect from their positions in the periodic table. 

Numerical Hartree-Fock calculations, free from basis set artifacts, have been used to establish that the ground state momentum densities of all the atoms and their ions can be classihed into three types [84,85]. Type I and III momentum densities are found almost exclusively in metal atoms He, N, all atoms from groups 1-14 except Ge and Pd, and all the lanthanides and actinides. These momentum densities all have a global maximum at p = 0 and resemble the momentum density shown in Fig. 19.3 for the beryllium atom. The maximum atp = 0 comes mainly from the outermost s-subshell, 2s in this case. Type I and III densities dilfer in that the latter have a secondary maximum that is so small as to be invisible on a diagram such as Fig. 19.3. Type II densities are the norm for non-metallic atoms and are found in Ge, Pd and all atoms from groups 15-18 except He and... 

Later developments of linear methods have been in the direction of self-consistent calculations of ground-state properties utilising local spin-density-functional formalism [1.51,52] for exchange and correlation. The basis of the self-consistency procedure was given in papers by Madsen et al. [1.53], Vouisen et al. [1.54] and Andersen and Jepsen [1.55], and was soon followed by results for the magnetic transition metals [1.56], the noble metals [1.57], some lanthanides [1.58], the actinides [1.59,60], and the 3d transition metal monoxides [1.61,62]. In this context one should also mention calculations of the electronic structure in transition metal compounds [1.63,64], A15 compounds [1.65,66], rare-earth borides [1.67], Chevrel... 

Nobelium is a member of the actinide series of elements. The ground state electron configuration is assumed to be (Rn)5fl47s2, by analogy with the equivalent lanthanide element ytterbium ([Kr]4fl46s2) there has never been enough nobelium made to experimentally verify the electronic configuration. Unlike the other actinide elements and the lanthanide elements, nobelium is most stable in solution as the dipositive cation No ". Consequently its chemistry resembles that of the much less chemically stable dipositive lanthanide cations or the common chemistry of the alkaline earth elements. When oxidized to No, nobelium follows the well-estabhshed chemistry of the stable, tripositive rare earth elements and of the other tripositive actinide elements (e.g., americium and curium), see also Actinium Berkelium Einsteinium Fermium Lawrencium Mendele-vium Neptunium Plutonium Protactinium Ruthereordium Thorium Uranium. 

They form part of a series in which the 5f electron orbitals become occupied in the ground state of the elements. In this sense they can be considered to be analogous to the lanthanides, in which the 4f orbitals are occupied in the ground state of the elements, and have been named the actinides. The actinides are listed in Table 16.1. They appear in the periodic table after element 88, radium, Ra, and end with element 103, lawrencium, Lr. 

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