Chemical Information Bulletin, Volume 62, Number 1, Spring 2010 Page: 30
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Chemical Information Bulletin Vol. 62(1) Spring 2010
ES: First let me say that I do not try to answer the 'in principle' question of whether chemistry can be reduced to
quantum mechanics. My emphasis has always been on the extent to which chemistry has in fact been reduced to
quantum mechanics. After all, who really knows what is possible in principle or what might be possible via a
future development in quantum mechanics? On the other hand, one can carefully examine whether present day
quantum mechanics does a good job of explaining in a more fundamental manner chemical phenomena such as
perhaps the form of the periodic table. I have claimed that although quantum mechanics gives a perfectly good ab
initio explanation of the lengths of periods of elements it does not fully explain the precise order of shell filling
which is summarized by the n + or Madelung rule which is familiar to anyone who has studied college or even
high school chemistry. And let me repeat-I am not claiming that such an explanation is not possible in principle
but just that nobody has yet succeeded in deriving this rule from the general principles of quantum mechanics.
SB: How do scientists working in individual disciplines relate to and treat each other? Are there disciplines
that are considered superior to other disciplines? When I was in college, I remember that physical chemists
were kind of elite. I can admit that this might have played a role for me choosing to do a Master's degree in
physical chemistry. I later spent most of my scientific career working in areas closer to organic chemistry
(lipids and fatty acids).
ES: Yes I agree with you, physical chemists and even more so theoretical chemists consider themselves somehow
superior to other specialists within chemistry. And theoretical physicists consider themselves even more superior.
Some of this one-upmanship is perhaps inevitable since the more theoretical the discipline, or the more one moves
towards physics, the more the scientist is operating at a more fundamental level. But more fundamental in the
literal sense should not be mistaken to mean superior since work at the less fundamental levels is just as essential
and in most cases remains indispensable. This is the paradox of reduction in all the sciences. We gain knowledge
of larger objects in terms of their microscopic components and the way they are organized and yet the detailed
knowledge must still be acquired by painstaking work at each of the appropriate levels in the scientific hierarchy.
SB: Another major theme that runs through your book concerns the nature of the element. This question
has puzzled Mendeleev and has significantly influenced his views. I would like to quote something from your
book: "Mendeleev held a dual view on the nature of elements, where they could be regarded as unobservable
basic substances and also as Lavoisier's simple substances at the same time. Mendeleev thus acknowledged
one of the central mysteries running throughout the long history of chemistry, which is the question of how,
if at all, the elements survive in the compounds they form when they are combined together. For example,
how can it be claimed that a poisonous gray metal like sodium is still present when it combines with a green
poisonous gas chlorine, given that the compound formed, sodium chloride, or common table salt, is white
and not only nonpoisonous but also essential for life?" How does the philosophy of chemistry deal with this
question and what diverging views exist in this area?
ES: There is a sense in which the question you are alluding to now lies at the very heart of philosophy of
chemistry. Let me use a well-worn example. When iron filings are mixed with sulfur, we obtain a physical
mixture of two elements. But when sodium reacts with chlorine, we obtain a compound in which the component
elements are not as easily recovered and also seem to have been radically transformed. To me the chemical change
is far more magical and far more mysterious. Understanding such chemical changes requires its own philosophical
approach. Mendeleev and others provided the beginnings of such an approach. We need to regard elements in two
senses, or maybe even three senses. First there is the element as a simple substance such as grey sodium. Then
there is the sodium, which is combined as in the case of sodium chloride. And thirdly there is what is common to
both of these forms of the element. The third option has been called "the element as a 'basic substance'", a
somewhat unfortunate terminology in view of the unintended reference to acid-base properties. Mendeleev
believed that it was this more fundamental, more philosophical sense of the elements that were represented on the
periodic table and not the other two senses. This is not so hard to appreciate. For example, the halogens, as simple
isolated substances, are rather different and they even display all three states of matter at room temperature. They
are not grouped together because of their similarities as simple substances. On the other hand, their compounds
with sodium, for instance, are all very similar. The properties of the combined elements appear to be more
decisive. Philosophers of chemistry are currently trying to clarify these distinctions, especially given the centrality
of the concept of 'element' in chemistry. There is a good deal of disagreement with some wanting to regard the
most fundamental sense of element as metaphysical, others-as merely abstract- and so on.30
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American Chemical Society. Division of Chemical Information. Chemical Information Bulletin, Volume 62, Number 1, Spring 2010, periodical, Spring 2010; Philadelphia, Pennsylvania. (https://digital.library.unt.edu/ark:/67531/metadc31514/m1/30/: accessed March 29, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; .