Chemistry Reference
In-Depth Information
The representational content of iconic models makes possible the testing of the
model not only for empirical adequacy, (does it enable successful predictions and
retrodictions of phenomena to be made?) but for ontological plausibility. Is there
something similar in the real world which not only behaves as the model is
imagined to behave but also is of the same general nature? Is there a molecular
double helix in the germ plasm sufficiently similar to that presented as a represen-
tation in the Watson-Crick model? Of course,
is a criterion that
comes in degrees and changes with the technology available. The work of Binnig
and Rohrer, cited above, is a nice example of the empirical establishment of the
authenticity of a model as a representation of something in the material world
by picking out individual atoms.
Given the above insights what can we say about the role of entitative concepts of
electrons in chemical understandings of atoms? The core of G. N. Lewis
'
sufficiently similar
'
s bonding
theory (
1926
) involves just such a conception of electrons as does the early Bohr
planetary model of the atom. And there lies the clue - it is not a mereological
fallacy to build a planetary
model
of the composition of atoms for heuristic
purposes of chemistry. How are we to assess the plausibility of models of the
internal constitution of atoms in relation to the role of this concept in chemistry?
Provided we use the model as a source of ideas about a mathematical representation
of the processes being modeled and resist material claims we are on sound ground.
Since we are not able to study the internal constitution of atoms by the kind of
methods we might use to study the internal constitution of a tape worm by
dissection and abstraction from what we observe, models of atomic
'
innards
'
cannot be analytical in the above sense. Nor can they be iconic, since to project
only one of the properties of product electrons back in to the structure of an atom is
to commit the second mereological fallacy. Clearly, the planetary electron hypoth-
esis, if taken seriously as a contribution to our knowledge of the internal constitu-
tion of atoms, is an example of that fallacy. The only remaining possibility is
Mulliken
'
s inspired proposal that we clearly disassociate ourselves from
electrons
'
'
and their orbits
.
It reminds us of the history of quantum chemistry from its beginnings in Bohrian
'
orbits
'
, but offers a purely formal model of the structure of chemical entities.
Mulliken
by proposing a pregnant new concept - that of the
orbital
'
'
'
s move from thinking in terms of orbits, an iconic model, to thinking in
terms of orbitals, a mathematical model, has the effect of retaining the electromag-
netic model of the atom, with all the apparatus of spin etc., as a valuable aid to
thinking about problems in chemistry at this level, but only heuristically. There can
be no inference as to that is how atoms are. That would be to commit the second
mereological fallacy.
'
References
Bennett MR, Hacker PMS (2003) Philosophical foundations of neuroscience. Blackwell, Oxford
Binnig G, Rohrer H (1986) Scanning tunneling microscopy. IBM J Res Dev 30:4
