A rigorous theory of valence

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Marco E. Ciriotti
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A rigorous theory of valence

Messaggio da Marco E. Ciriotti » lun 04 set, 2023 9:47

▪ Brown, I.D. (2023): A rigorous theory of valence. Structural Chemistry, 34, 361–389.

Many sciences are described by two conceptually different but complementary theories, one visual and insightful the other better suited to computation. Chemistry has a powerful computational theory in quantum mechanics, but its visual and insightful theory of valence has never been properly developed. The rigorous theory of valence described here takes the atom as its fundamental particle. As the theory has no knowledge of the atom’s internal structure, the valence is not associated with the electron, hence it is free to adopt fractional values. Each atom is characterized by two experimental properties: its valence determined from the compositions of observed compounds, and its size determined from its observed coordination numbers. These two properties are able to describe a surprising amount of chemistry. The amount of valence an atom typically uses to form a bond determines both the conditions under which bonds can be formed and their resulting properties. A valence definition of electronegativity removes the need to distinguish between ionic and covalent bonds by defining the more nuanced concept of bond polarization, clearing up much of the confusion found in popular bonding models. The theory is compatible with the physical picture provided by quantum mechanics but not with the physically unrealistic ionic model. It can be used for analyzing, modeling, and teaching of chemical structure and reactivity, but having no knowledge of the internal structure of the atom it cannot be used to calculate energies or any of the properties that depend on the energy; for that quantum mechanics must be used.
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»


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