Electron configuration of lanthanides

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 ... 

This effect originates in the various f electron configurations of lanthanides and actinides. This effect is based on the correlation observed between the full pattern of the effect and the sequence of values of the L quantum number [52]. The correlation consists of the occurrence of the same double symmetry in (a) the series of L quantum number values of the ground terms of f element ions and (b) the sequence of relatively stabilized or destabilized f electron configurations (i.e.) the double-double effect. Accordingly... 

Electronic Configuration of Lanthanide Atoms in the Ground State... 

It should be pointed out that not all the ions discussed here are affected by the outer fields. In fact, lanthanide ions may be affected by solvents or coordination fields in chemical reactions. For example, E and E will change because of the coordination effect of water or organic molecules in an extraction. In addition, the amount of change would be different in different media. The tetrad effect would thus be different in different systems. The tetrad effect not only relates to the electronic configurations of lanthanide elements but is also affected by the surrounding conditions. Currently it is still not possible to predict the tetrad effect or to calculate it quantitatively. Tetrad effect theory still needs to be improved and further data need to be accumulated. 

There is no single best form of the periodic table since the choice depends on the purpose for which the table is used. Some forms emphasize chemical relations and valence, whereas others stress the electronic configuration of the elements or the dependence of the periods on the shells and subshells of the atomic structure. The most convenient form for our purpose is the so-called long form with separate panels for the lanthanide and actinide elements (see inside front cover). There has been a lively debate during the past decade as to the best numbering system to be used for the individual... 

THE ELECTRON CONFIGURATIONS OF GASEOUS ACTINIDE AND LANTHANIDE ATOMS... 

In many cases the relationships have not been so easily interpreted. For many salts, having transition metal cations, no unequivocal trend can be found (138). The electronic configuration of the cation has also been found to have an effect in this direction. However, the exact opposite trend has been reported for other compounds such as vateritetype lanthanide borates, the vibrational frequencies increase with increasing effective nuclear charge of the cation (186, 187). All this goes to indicate how comphcated this problem is. 

The lanthanide elements are the 15 elements from lanthanum to lutetium. Both La and Lu have been included to allow for the different versions of the Periodic Table, some of which position La in Group 3 as the first member of the third transition series and others that place Lu in that position. If Lu is considered to be the first element in the third transition series, all members of that series possess a filled shell 4f14 configuration. The outer electronic configurations of the lanthanide elements are given in Table 8.1. 

Table 8.1 The outer electronic configurations of the lanthanide elements they all possess a 6s2 pair of electrons...

The properties of the liquid lanthanide trihalides depend strongly on the atomic number of the halide. The variation in the heat capacity of the lanthanide fluorides indicates a strongly ionic behaviour of the melts with a concomittent irregular trend related to the electronic configuration of the lanthanide ions. In the lanthanide chlorides, bromides and iodides the trend becomes systematically more constant, indicating an increasing molecular nature of the melts. 

The striking characteristics of the lanthanide higher oxides are rooted in the electronic structure of Ce, Pr, and Tb atoms. The lanthanide elements located in the third group of the periodic table have a normal 3+ valence state and the normal oxides have the R2O3 formula. Due to the special electron configurations of Ce... 

On the other hand, the specific electron configuration of the nitrogen allows a chemistry comparable to that of the ubiquitous cyclopentadienyl ligand and this offers an opportunity to get within distance of the all-powerful lanthanide alkoxide chemistry. The introduction of unsaturated monoanionic ligands like substituted pyrrols is currently in progress. In the last ten years there has also been a steadily growing interest in polycyclic amides, e.g., porphyrins and phthalocyanines. 

Lanthanum, the first member of lanthanides has the configuration of 5d)6s2 and next member cerium, has 4fi6s2 while the next element praseodymium has the configuration 4f3 6s2. Although lanthanum itself does not possess any 4/electrons, it is customary to include this element in the series. The electronic configurations of the elements with fully filled (// and half-filled (f7)/-orbitals are relatively more stable. 

The mechanism for polymerization of propylene with heterogeneous catalysts is very similar to that of ethylene. Studies with a homogeneous catalyst of a lanthanide element provided early mechanistic evidence. The complex used in these studies was 6.15. In 6.15 lutetium is in a 3+ oxidation state and has the electronic configuration of 4fu. In other words Lu3+ has a full/shell and 6.15 is a diamagnetic complex. 

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