Comprehensive Definition of Oxidation State

Provisional Recommendations are drafts of IUPAC recommendations on terminology, nomenclature, and symbols, made widely available to allow interested parties to comment before the recommendations are finally revised and published in IUPAC’s journal Pure and Applied Chemistry. 

Oxidation state (OS) is a simple numerical attribute of an atom in a compound, which aids the systematic descriptive chemistry of the elements, scales trends in properties, and tracks key chemistry changes in reactions. Lacking a comprehensive definition, OS has so far been defined via algorithms for its calculation or with postulated values. This document provides a definition of OS based on ionic approximation of chemical bonds. Associated with the definition’s underlying principle of bond-electron allegiance, two general algorithms are outlined for OS determination in a molecule, ion, or a solid, described by a Lewis formula or a bond graph. Typical origins of ambiguous OS values are pointed out, and the relationship between OS and the d-electron configuration of transition metals is commented on.

Comments by 31 May 2016

Pavel Karen <>

See project 2008-040-1-200 to access full text.

See Provisional Recommendations currently under review.