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In-Depth Information
as particulate phenomena were parts of the atoms from which they were sourced.
The principle behind this strong claim is something like this: it is at least a
necessary condition for the products of an analysis to be ascribable to the whole
from which they came as its parts that they share the same general criteria of
individuation and identity. The dual nature of electrons as having particulate and
undulatory attributes, at least at the level of chemical explanations, distinguishes
them from atoms and from molecules. Is Bohr
s inference to the planetary electron
conception of the atom not just a superceded image of the nature of atoms, but also a
mereological fallacy? More radically still, inspired by Mulliken
'
s interpretation
of quantum chemistry, should we not go further down this line and query the
claim that molecules are
actually
structures of atom-cores? But that radical step
is blocked by the work of Binnig and Rohrer.
To say that such and such an atom has this number of electrons in that shell
and to use that hypothesis to account for some of its chemical properties, does not
entail that there is a cloud of little charged particles orbiting the nucleus. But what is
its status? According to the line of reasoning developed in this paper it can be no
more than a mereological
model
of this kind of atom. It can hardly be disputed that
knowledge of the physics of the subatomic level of reality plays an important part in
the practice of chemistry. It is therefore not surprising that philosophical issues
in the physics of that domain should also play a part in the philosophy of chemistry.
What makes us think in terms of entities when we draw inferences about the
electron yielding properties of atoms? Experiments can be devised to display
the presence of electrons as tracks in cloud chambers, photographic emulsions
and computer simulations (Harr
´
1990
).
There are no orbits because there are no particulate electrons absent such devices
as cloud chambers, but in what sense are there Mulliken orbitals? The way that
Mulliken
'
s proposal resolves the tensions in building a basic theory of chemical
bonding on the second mereological fallacy can be seen in analyzing his insight in
the light of the various procedures of model making and the different kind of
models that ensue.
'
8.6.1 Models in Science
There are two kinds of models in use in the sciences (Harr´
2006
). They are
differentiated by the relation of the model to that which it serves to model. A
model has a
subject
- that which it is a model
of
, and it has a
source
- that which is it
modeled
on
.
For some models the subject is also the source of the content of the model.
These are the analytical models which are usually used to display the structure of
some complex entity and are derived from that entity by abstracting relevant
features. There may a several different analytical models of the same entity, for
example the many geological models of the earth each created by abstracting only
certain features, say geological strata as compared with the core and the mantle.
