Chemistry Reference
In-Depth Information
This implied that, in the case of primary groups, no differentiation between the
congeners was possible anymore on the basis of their atomic weights. Otherwise
stated, while
secondary elements
could still be characterised by their atomic
weights,
primary elements
, on the other hand,
could no longer be characterised
by the atomic weight
!
11.1.12
Internal Differences of Matter
The question naturally presented itself as to how one should differentiate between
primary elements. According to Mendeleev, these elements were characterised by
“
internal differences of matter
”.
47
The reason for the differences “is no longer the
size and the weight of the atom,” he said, “but obviously some other
internal
differences in the matter
, constituting the atoms of these similar elements”.
48
This was comparable in some respects with
isomeric substances
, as well as with
metameric compounds
, which were defined by Mendeleev as having “the same
weight of particle [i.e. molecular weight] but in which the distribution of parts or
atoms inside the particle is undoubtedly not identical”.
49
While Mendeleev
clearly stated that “elements of a similar nature, with similar atomic weights [i.e.
primary elements], are somewhat similar to metameric compounds”,
50
it is not
completely clear whether he actually believed in the
complexity of atoms
. After all,
whereas Mendeleev referred to the “internal differences in the matter,
constituting
the atoms
”, Mendeleev also mentioned the “internal
arrangement of atoms
”ata
certain point. Did he mean that the atoms were different due to an internal
arrangement (thus believing in the complexity of atoms), or was he alluding to an
internal difference in the arrangement of atoms inside a molecule? In any case,
whether Mendeleev believed in the complexity of atoms or not, he definitely
believed in the existence of atoms during the period 1869-1870. At that time,
Mendeleev was giving his thoughts about the periodic system free rein. He was still
prepared to accept the atomic hypothesis and he believed in both the chemical
and physical atom.
In sharp contrast with the above-mentioned statement, the famous Mendeleev
historian, Michael Gordin, claimed in his topic on
Dmitrii Mendeleev and the
Shadow of the Periodic Table
that “it does not follow [
] that Mendeleev must
have been thinking in terms of physical atomism when he conceived his system.
[
...
s scepticism toward atomism sharply emphasises the difference
between the present-day interpretation of the periodic system and Mendeleev
...
] Mendeleev
'
s
'
views of 1869. [
...
] For Mendeleev, any atoms that might exist had
absolutely no
47
Loc. cit. English translation by Trifonov (1970), op. cit., p. 38. (note 36) Emphasis added.
48
Loc. cit. English translation by Trifonov (1966), op. cit., p. 28. (note 29)
49
Loc. cit.
50
Loc. cit.
