Chemistry Reference
In-Depth Information
11.1.9 The Rare Earth—Transition Metal Analogy
As a consequence of fixing all his attention on the
Attempted System
, Mendeleev
immediately recognised how the two primary groups, {Ce, La, Di} and {Er, Yt}, at
the bottom part of his system helped in connecting the periods of the main core.
It thus seemed that these primary groups were furnished with a
transitional function
as well. Due to the fact that both the transition metal groups (iron, palladium and
platinum group) and the rare-earth groups (cerium and erbium group) exhibited a
transitional function, Mendeleev quickly emphasised the similarity between these
two sets of groups. Mendeleev first voiced these ideas in his 1869 article
On the
Correlation between the Properties of the Elements and Their Atomic Weights
,
where he wrote:
Perhaps for this reason [the] positions [of the iron group, the palladium group, and the
platinum group] will have to be changed and, were they to be placed in the lower rows
instead of the upper rows, then one would obtain three columns here which would, in many
respects, exhibit
similarities
: one column containing cobalt, nickel, chromium, manganese,
and iron [as well as Er, Yt, and In]; a second column containing cerium, lanthanum, and
didymium, palladium, rhodium, ruthenium, and lastly, a third columns containing plati-
num, iridium, and osmium.
28
The rare earth—transition metal analogy was further exemplified by Mendeleev in
his article
Concerning the Atomic Volumes of Simple Bodies
(presented on
23 August 1869). Referring to the work of Wiedemann, Mendeleev emphasised
the similarity in magnetic properties between the elements of the cerium group and
of the iron group. Not only were all these elements “magnetic in their compounds”,
“their atomic magnetism [remained] similar when passing from one analogue to
another.”
29
Repeated references to the rare earth—transition metal analogy were
also made in his article
On the Quantity of Oxygen in Metal Oxides and on the
Valency of the Elements
(presented on 2 October 1869) and in the second volume of
his
Osnovy khimii
, published in March 1870.
11.1.10 Undermined Periodicity
A fourth and last consequence of the existence of primary groups was their
problematic nature—undermining both the periodic law and the characterisation
of elements as being defined by their atomic weight. Let us start with the subversion
of periodicity. Mendeleev explained that “the arrangement of elements [
]
according to the magnitude of their atomic weights corresponds to their
so-called valencies and, to a certain degree, to the differences in their chemical
...
28
Mendeleev (1869b/t), op. cit., p. 30. (see note 16) Emphasis added.
29
Mendeleev, D. I. “Concerning the Atomic Volumes of Simple Bodies.” In
Arb. IIKongr. Russ.
Arzt. Naturf
., 1869e. English translation by Trifonov, D. N. “Mendeleev and the Rare Earths.” In
Problems
in the Study of Rare Earths
, 28.
Jerusalem:
Israel Program for Scientific
Translations, 1966.
