J. P. Redfern and J. E. Salmon
Battersea College of Technology London. England
I
I
Two factors are generally ignored in presenlations of the periodic table; these are (1) the fact that the lanthanons and the elements following actiuinm are hoth transition elements and, by virtue of their unfilled f orbitals, inner transition elements as well; (2) there are a number of elements which by virtue of their chemistry cannot adequately be represented by placing them in only one position in the periodic table. To be included in this category are hydrogen and the early members of the actinons. Hydrogen s h o m family likenesses to the alkali metals, by virtue of its electronic configuration and certain aspects of its chemistry, and to the halogens, by virtue of certain chemical similarities. See Gnggenheim (1).
Classification of the Elements
In the long form of the table proposed by Coryell (2) there is an attempt to indicate this duality by means of hoth solid and broken tie-lines, but the result lacks simplicity. The form of the table which we propose here clearly reflects the first feature above, in that the resemblance of the transition elements of Group III-A to the lanthanons and actinons is indicated, while by reason of the vertical arrangement there is, a t the same time, a suggestion that the inner transition series elements are somewhat different. In addition an indication of the electronic configuration, as determined spectroscopically, is more nearly approached than in conventional tables. The duality of the elements hydrogen, thorium, protoactinium, and uranium may be represented by placing these elements in two positions clearly joined by a horizontal line. By placing thorium, protoactinium, and ura.nium in two positions the arguments for and against the inclusion of these elements in a second rare earth series can he very readily appreciated. One may extend this principle by indicating the other oxidation states of the lanthanons and actinons, which brings out the similarity of the patterns exhibited by the two series. In order that the principle of duality is not submerged by this detail the other oxidation states of the lanthanons and actinons have been enclosed in brackets. This method of presentation retains the characteristic features of the generally accepted form of the periodic classification which, according to Clifford (S), is a prerequisite to ready acceptance. However, in this modified form the tahle clears away a number of existing anomalies, gives a clearer representation of the known facts, and is offered in the hope that it can he used for instructional purposes. Liferatwe Cited (1) GUQGENAEIM, E. A,, J. Royal Insl. Chem., 84, 413 (1960). L ~D., J. CAEM.EDUC., 29.26 (1952). (2) C O R Y E C. (3) CLIFFORD, A. A,, Nature, 186, 154 (1960).
Volume 39, Number I, January 1962
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