Chemical equation
model of chemical reaction in form of a written equation
A chemical equation is the symbolic representation (notation) of a chemical reaction in the form of symbols and chemical formulas. The reactant entities are given on the left-hand side, and the product entities are on the right-hand side with a plus sign between the entities in both the reactants and the products, and an arrow that points towards the products to show the direction of the reaction. The chemical formulas may be symbolic, structural (pictorial diagrams), or intermixed. The coefficients next to the symbols and formulas of entities are the absolute values of the stoichiometric numbers. The first chemical equation was diagrammed by Jean Beguin in 1615.
Structure
A chemical equation (see an example below) consists of a list of reactants (the starting substances) on the left-hand side, an arrow symbol, and a list of products (substances formed in the chemical reaction) on the right-hand side. Each substance is specified by its chemical formula, optionally preceded by a number called stoichiometric coefficient. The coefficient specifies how many entities (e.g. molecules) of that substance are involved in the reaction on a molecular basis. If not written explicitly, the coefficient is equal to 1.
This brief starts where responsible research should: with the source description of “Chemical equation” as model of chemical reaction in form of a written equation. Everything that follows is an evidence route, not borrowed authority.
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The subject matters to the science & nature register because the source frames it as model of chemical reaction in form of a written equation. Its deeper value depends on whether names, dates, institutions and citations support that framing.
The date and method of observation matter as much as the stated conclusion, especially where classification or consensus has changed. The source revision retrieved here is dated Sep 8, 2026. The linked authority identifier is Q182527. The Library of Congress control number is sh85022909. 1 of 1 selected statements include explicit references; 1 carry qualifiers and 0 use preferred rank. The first chronological checks are 1615.
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This entry incorporates text from “Chemical equation” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.