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Valency
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Abstract
The concept of valency is refined and developed. Three types of valency are distinguished : primary or classical, coordinate, and nonclassical. The first relates to simple compounds and to the components of multiple ones, the second to coordination compounds, and the third to transition-metal carbonyls and similar species. Each type is defined, evaluated, and applied to the prediction of the atomic composition of compounds. Relations are established between valency and bond number, charge number, oxidation number, and number of d or f electrons.
The resulting theory has several advantages over electronic theories of bonding. It is simpler, it applies to transition-metal compounds as well as to main-group ones, and it enables chemical formulae to be predicted without reference to the nature of the bonding (e.g. it does not presuppose that metal oxides are ionic, or that atoms in hypervalent compounds do or do not use d orbitals). It also provides a classification of substances that avoids the artificiality involved in the current use of oxidation number, and brings together species that are presently classified separately [e.g. HgI2 and HgIICl2; Fe0(CO)5, FeII(CO)4Cl2, and Fe–II(CO)2(NO)2].
Keywords (Audience):
Second-Year UndergraduateKeywords (Domain):
Organic ChemistryKeywords (Subject):
Valence Bond TheoryCiting Articles
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This article has been cited by 3 ACS Journal articles (3 most recent appear below).
Valence, Covalence, Hypervalence, Oxidation State, and Coordination Number
Derek W. SmithJournal of Chemical Education2005 82 (8), 1202Valence, Covalence, Hypervalence, Oxidation State, and Coordination Number
Derek W. SmithJournal of Chemical Education2005 82 (8), 1202It is argued that the terms valence, covalence, hypervalence, oxidation state, and coordination number are often confused and misused in the literature. It is recommended that use of the term valence, and its associated terminology, should be restricted ...
Quantifying Molecular Character
P. G. NelsonJournal of Chemical Education2000 77 (2), 245Quantifying Molecular Character
P. G. NelsonJournal of Chemical Education2000 77 (2), 245Wells and Jensen's classification of substances according to structure type is quantified, enabling substances having an intermediate structure to be classified precisely. Jensen's concept of the "degree of nonmolecularity" of a substance and the opposite ...
Uncommon Oxidation Numbers of Nonmetals
Wayne P. AndersonJournal of Chemical Education1998 75 (2), 187Uncommon Oxidation Numbers of Nonmetals
Wayne P. AndersonJournal of Chemical Education1998 75 (2), 187Common oxidation numbers of nonmetals can be predicted from their electron box diagrams. Conditions necessary for atoms to achieve such common oxidation numbers are described. The presence of an odd number of electrons, homonuclear bonds, or attached ...
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History
- Received: August 03, 2009
ACS
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