Lanthanide
The chemical Série of the lanthanides is made up of the metals of transition located between the element S from atomic numbers 57 (the) at 71 (Lu) included. Those are also called more commonly rare earths , even if this term is not very suitable since apart from the Prométhium, they are relatively abundant. In lower part of them, one finds the series of the Actinide S. lanthanides and the Actinide S belong to the group of metals of the block F.
Lanthanides are elements whose orbital S 4 F are, in general, partially or completely filled, only the other elements having electrons of valence F , are the Actinide orbital S. These F are relatively interns: these electrons are thus not very available to form covalent bonds, which explains why the ions of the elements of these series, form complex without preferences on the level of their geometry of coordination.
The Lanthane, the first element of the series to which it gives its name, are in the 3rd column of periodic classification, it is thus not surprising that it is stable with the Step oxidation +III. What is remarkable is that all the elements going of the with Lu support the state of oxidation +III with a uniformity not-equalized in the periodic Tableau. Certain lanthanides can also exist with oxidation the step +II (in particular Have) or +IV (in particular What is in the 4th column). Thus the (III) and This (IV) have the electronic structure of the rare Gas preceding them, Xe: their maximum oxidation step corresponds to the number of the column of periodic classification where they are. Lanthanides heavier than This oxidize with difficulty with the oxidation step +IV. This is explained by the fact why orbital the F is relatively interns: it is difficult to remove electrons F . Lanthanides are very electropositive and the Ln3+ cations are hard cations (according to the theory HSAB).
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