Title: stoichiometric number
Long Title: IUPAC Gold Book - stoichiometric number
DOI: 10.1351/goldbook.S06025
Status: current
Index: quantity

Definition
A chemical reaction of known stoichiometry can be written in general as: \[a\rm{A}\,+\,b\rm{B}\,+\,...\rightarrow\,...\,+y\rm{Y}\,+\,z\rm{Z}\] For the reaction products Y and Z the numbers \(y\) and \(z\) are known as the stoichiometric numbers, \(\nu _{\rm{Y}}\) and \(\nu _{\rm{Z}}\), for Y and Z respectively. For the reactants the stoichiometric numbers are the negatives of the numbers appearing in the equation; for example the stoichiometric number \(\nu _{\rm{A}}\) for the reactant A is \(-a\). In other words, the stoichiometric numbers are positive for products and negative for reactants.

Related Terms
- stoichiometric: https://goldbook.iupac.org//terms/view/S06021
- stoichiometry: https://goldbook.iupac.org//terms/view/S06026

Sources
- Green Book, 2nd ed., p. 42 (https://goldbook.iupac.org/files/pdf/green_book_2ed.pdf)
- PAC, 1996, 68, 149. 'A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC Recommendations 1996)' on page 187 (https://doi.org/10.1351/pac199668010149)
- PAC, 1996, 68, 957. 'Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)' on page 993 (https://doi.org/10.1351/pac199668040957)

Related Reference
- PAC, 1996, 68, 1167. 'Pesticides report 36. Glossary of terms relating to pesticides (IUPAC Recommendations 1996)' on page 1168 (https://doi.org/10.1351/pac199668051167)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/S06025/html
- json: https://goldbook.iupac.org/terms/view/S06025/json
- xml: https://goldbook.iupac.org/terms/view/S06025/xml

Citation: Citation: 'stoichiometric number' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.S06025
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Accessed: 2026-04-27T15:59:57+00:00