A chemical equation is a representation of a chemical reaction, showing the initial substances (reactants) and final substances (products). Because matter is conserved in a chemical reaction, an equation is balanced if the number of atoms of each element on the reactant side of the equation is equal to the number of atoms of that same element on the product side of the equation; an equation is balanced by placing coefficients in front of the formula of each reactant and product (when the coefficient is one, the coefficient is omitted).

1. Assign a coefficient to one to the most complicated species in the reaction (the substance with the largest number of elements).
2. Identify an element that appears in only one species for which the coefficient is not yet determined and assign a coefficient to that species that will balance the number of atoms of that element on the two sides of the equation. Continue until a coefficient is assigned to each species.
3. If it is necessary to assign fractional coefficients to one or more species, eliminate fractional coefficients by multiplying each coefficient of the equation by the smallest integer that will eliminate the fractions.