Geochemistry ionic properties

The REE all have very similar chemical and physical properties. This arises from the fact that they all form stable 3+ ions of similar size. Such differences as there are in chemical behaviour are a consequence of the small but steady decrease in ionic size with increasing atomic nunAer. This is illustrated for ions m eight-fold coordination state in Table 4.4. These small differences in size and behaviour are exploited by a number of petrological processes causing the REE secies to become fractionated relative to each other. It is this phenomenon which is used in geochemistry to probe into the genesis of rock suites and unravel petrological processes. 

The systematic study of electrolyte solutions by van t Hoff and Arrhenius (1887) established physical chemistry as a scientific discipline. Electrolytes are important not only in solution chemistry and in the chemistry of electrode processes, but also in geochemistry and oceanography and in many areas of biophysics and biochemistry. Salt solutions , as they are often referred to by chemists, are ubiquitous they are easily handled in the laboratory and their properties accurately measured. Reams of experimental data on these solutions have been collected but their explanation and correlation in terms of the molecular (or microscopic) properties of the system continue to present major challenges to theoretical chemists. This has also lead to the formulation of sophisticated new techniques in statistical mechanics and the extensive use of computer simulation to study ionic fluids. 

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