Summary
The distribution of the peripheral electrons in the atoms is not always sufficient in itself for the chemical characterisation of the elements and their classification in the periedic system. In making this classification one ought to take into consideration principally thefundamental chemical properties, namely the maximum valency, the relative stabilities of the various oxidation states, etc. Such considerations exclude the possibility of gathering the elements of atomic numbers 89–98 into a single family. A complex evolution of chemical properties is rather observed in the 7th period. It can be summarised as follows:
(1) The elements from Fr to U ought to be arranged normally in the vertical groups I–VI.
(2) The three following elements Np, Pu, Am have strict analogies with U and form auranide group with it.
(3) Starting with Cm, there is a predominance of valency III and the appearance of acuride group whose proprieties seem to be close to those of the lanthanides Gd, Tb, Dy...
This arrangement is in agreement with the most recent physical measurements on the electronic distribution.
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References
Voir, par exemple:G. Seaborg, Nucleonics5, 16 (1949).
M. Haïssinsky, J. Chem. Soc. London1949, Suppl. 2, 241; voir aussi: J. Chim. Phys.47, 415 (1950).
Cette hypothèse est particulièrement contredite par la chimie de Pa. Ses partisans semblent souvent la négliger ou considèrent par exemple que «la chimie de Pa en solution reste en grande partie un mystère» (J. J. Katz etW. M. Manning, Ann. Rev. Nucl. Sci.1, 250 [1952]). En réalité, cette chimie n'est pas plus mystérieuse que celle des homologues Nb et Ta; mais elle présente de grandes difficultés dues à la propriété commune de ces éléments, de ne pas avoir un comportement autonome, lorsque l'un se trouve en présence d'un excès d'un de ces deux autres ou d'un élément apparenté chimiquement (Zr, Ti, etc.). Pour plus de détails, voirM. Haïssinsky etG. Boussières, Bull. Soc. chim. France18, 146, 557 (1951).
S. Thompson, B. Cunningham etG. Seaborg, J. Amer. Chem. Soc.72, 2798 (1950).
K. Street, S. Thompson etG. Seaborg, J. Amer. Chem. Soc.72, 4832 (1950).
J. Dawson, Nucleonics10, 39 (1952).
W. Zachariasen, Acta crist.5, 19 (1952); Ann. Rev. Phys. Chem.3, 359 (1952).
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Haïssinsky, M. La place des éléments transuraniens dans le système périodique. Experientia 9, 117–120 (1953). https://doi.org/10.1007/BF02178348
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DOI: https://doi.org/10.1007/BF02178348