Glossary of Words

Summary and Key Ideas

Writing and Balancing Chemical Equations

Chemical equations are symbolic representations of chemical and physical changes. Formulas for the substances undergoing the change (reactants) and substances generated by the change (products) are separated by an arrow and preceded by integer coefficients indicating their relative numbers.

Balanced equations are those whose coefficients result in equal numbers of atoms for each element in the reactants and products. Chemical reactions in aqueous solution that involve ionic reactants or products may be represented more realistically by complete ionic equations and, more succinctly, by net ionic equations.

Glossary

Balanced equation

chemical equation with equal numbers of atoms for each element in the reactant and product

Chemical equation

symbolic representation of a chemical reaction

Coefficient

number placed in front of symbols or formulas in a chemical equation to indicate their relative amount

Complete ionic equation

chemical equation in which all dissolved ionic reactants and products, including spectator ions, are explicitly represented by formulas for their dissociated ions

Molecular equation

chemical equation in which all reactants and products are represented as neutral substances

Net ionic equation

chemical equation in which only those dissolved ionic reactants and products that undergo a chemical or physical change are represented (excludes spectator ions)

Product

substance formed by a chemical or physical change; shown on the right side of the arrow in a chemical equation

Reactant

substance undergoing a chemical or physical change; shown on the left side of the arrow in a chemical equation

Spectator ion

ion that does not undergo a chemical or physical change during a reaction, but its presence is required to maintain charge neutrality