of molecules. It should be pointed out that Bohr theory has also additional defect.
Suppose that the Bohr calculation of the bond energy could be improved by using,
for example, the more accurate starting numerical parameters. The result would be
better, but not substantially. It would still be far from the experimental observation.
Substantial improvement of this theory that could give more accurate values of
energy of chemical bond is not possible, because it is limited by the basic
classical-mechanical axiomatics. New paradigm, which must reshape the theory in a
way that it would be able to predict physical observations in broader sense, is in
sight. The new system should be, by its epistemology, open, what means that the
calculations should have the form to be iteratively refined until they will describe
experimental observations with satisfactory accuracy.
As it is known from the history of science, especially from the history of physics,
this new system is quantum mechanics, which has been for the first time formulated
by Werner Heisenberg (1925), and in year latter Erwin Schrödinger. Heisenberg’s
and Schrödinger’s quantum mechanics is in principle a sort of
mathematical-metaphysical trick that has not only changed the fundamental world
view, but also the general way of thinking. In continuation of this lecture, I will try
to demonstrate how almost analogous scientific revolution with similar metaphysical consequences has appeared in chemistry ten years before it has aoppeared
in physics. Since these lectures are focused on philosophy of chemistry, I will focus
your attention to the paradigmatic change within chemical conceptual systems.
Partially, I would try to refer to the common conceptual ideas with physical
quantum mechanics.
My represented picture of the science, which is positioned between physical and
chemical poles, will be reflected also in this scientific revolution. As the discovery
of atoms has triggered the polarization between scientists in their opinion about the
physical reality of atoms (physical and chemical atoms in the tenth Lecture), the
description of electrons can also have its physical and chemical version.
Heuristic concept of “chemical electrons”, which has helped not only in
explanation and prediction of geometries (shapes) of molecules but also in
description of a series of other properties, especially their chemical behaviour
represented within the frame of the reaction mechanism concept, has appeared as an
extension of the Thomson model. Hundred years ago, 1916, Gilbert Newton Lewis
has published in the Journal of the American Chemical Society the paper entitled
The Atom and the Molecule [1] in which chemical bound is described as a pair of
electrons. The basic idea in this Lewis approach is that electrons do not have
identity (in contrast to Thomson’s concept about electrons). Thus, in common
electron pair in chemical bond it is not possible to determine the origin of the
particular electron. Such an approach, as well as the opening of the problem of
identity, is characteristics of the later developed quantum mechanics.
Lewis idea about electron pairs is the direct consequence of the previously
described Abegg octet rule. As I have mentioned, Thomson has already suggested
that electrons are in atoms divided in two groups, the inner electrons, and the outer
electrons which are responsible for the formation of chemical bond. Inspired with
the octet rule, Thomson has proposed the hypothesis that the maximal number of
122
12 Limits of Structural Theory
Suppose that the Bohr calculation of the bond energy could be improved by using,
for example, the more accurate starting numerical parameters. The result would be
better, but not substantially. It would still be far from the experimental observation.
Substantial improvement of this theory that could give more accurate values of
energy of chemical bond is not possible, because it is limited by the basic
classical-mechanical axiomatics. New paradigm, which must reshape the theory in a
way that it would be able to predict physical observations in broader sense, is in
sight. The new system should be, by its epistemology, open, what means that the
calculations should have the form to be iteratively refined until they will describe
experimental observations with satisfactory accuracy.
As it is known from the history of science, especially from the history of physics,
this new system is quantum mechanics, which has been for the first time formulated
by Werner Heisenberg (1925), and in year latter Erwin Schrödinger. Heisenberg’s
and Schrödinger’s quantum mechanics is in principle a sort of
mathematical-metaphysical trick that has not only changed the fundamental world
view, but also the general way of thinking. In continuation of this lecture, I will try
to demonstrate how almost analogous scientific revolution with similar metaphysical consequences has appeared in chemistry ten years before it has aoppeared
in physics. Since these lectures are focused on philosophy of chemistry, I will focus
your attention to the paradigmatic change within chemical conceptual systems.
Partially, I would try to refer to the common conceptual ideas with physical
quantum mechanics.
My represented picture of the science, which is positioned between physical and
chemical poles, will be reflected also in this scientific revolution. As the discovery
of atoms has triggered the polarization between scientists in their opinion about the
physical reality of atoms (physical and chemical atoms in the tenth Lecture), the
description of electrons can also have its physical and chemical version.
Heuristic concept of “chemical electrons”, which has helped not only in
explanation and prediction of geometries (shapes) of molecules but also in
description of a series of other properties, especially their chemical behaviour
represented within the frame of the reaction mechanism concept, has appeared as an
extension of the Thomson model. Hundred years ago, 1916, Gilbert Newton Lewis
has published in the Journal of the American Chemical Society the paper entitled
The Atom and the Molecule [1] in which chemical bound is described as a pair of
electrons. The basic idea in this Lewis approach is that electrons do not have
identity (in contrast to Thomson’s concept about electrons). Thus, in common
electron pair in chemical bond it is not possible to determine the origin of the
particular electron. Such an approach, as well as the opening of the problem of
identity, is characteristics of the later developed quantum mechanics.
Lewis idea about electron pairs is the direct consequence of the previously
described Abegg octet rule. As I have mentioned, Thomson has already suggested
that electrons are in atoms divided in two groups, the inner electrons, and the outer
electrons which are responsible for the formation of chemical bond. Inspired with
the octet rule, Thomson has proposed the hypothesis that the maximal number of
122
12 Limits of Structural Theory