Electron Configuration. Term Values

Term values for electronic states of PH which have been studied experimentally and theoretically are compiled in Table 1. For details see below. 

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This is the origin of the various values for self-exchange rate constants. We may now attempt to rationalize some of these in terms of the /-electron configurations of the various oxidation states. Consider the self-exchange rate constants for some iron complexes. 

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 ... 

One finds that states of a given electronic configuration that have the same values of L and 5 have the same energy eigenvalue for the Hamiltonian H°+ H such states are said to belong to the same term. Different terms... 

Since maximum 5 arises from having the greatest possible number of electrons unpaired, the free-ion ground term of a configuration is that with the highest value of L consistent with the maximum possible number of unpaired electrons. The largest value of L is obtained as the maximum value... 

The evaluation of the quantitative aspects of the splitting involves calculations which become quite involved for the terms of higher L value from multi-electron configurations. We only present the results for the ground terms of the d configurations. The splitting patterns of these are set out in Figure 9. 

In LS coupling the energy levels of two-electron configuration will be characterized according to Eq. (11.2) by intermediate quantum numbers L, S and resultant momentum J. Usually, instead of LSJ, the notation 2S+1Lj is utilized. Quantum numbers L and S denote the term of the multiplicity 2S + 1, whereas J describes the so-called fine structure (levels) of the term. Each level in accordance with the values of M = —J,—J + 1,...,J consists of 2J + 1 states. The number of levels of the term equals 2S + 1, i.e. its multiplicity, if L > S, and equals 2L + 1, if L half-integer) positive values (including L = S = J = 0), however, usually the capital letters of the Latin alphabet are utilized to denote L (as well as small ones for /) in accordance with... 

The spectra of complexes with configurations other than dx and d9 are rather complicated and we cannot always obtain values of A directly. Racah has developed methods for the interpretation of the spectra of transition-metal ions in terms of A and a number of other parameters. This book is not concerned with the detailed origin and interpretation of these parameters suffice it to say that one of the parameters, B, is a measure of the electron repulsion terms in the valence shell of the metal ion. It is found that the value of B is a function of the ligands which surround the metal ion, and that it is always lower in a complex than in the free metal ion. In other words, co-ordination of a ligand to a metal ion results in a lowering of electron-electron interactions within the valence shell. Just as we... 

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