Why do the coefficients of an elementary step equal the reaction orders of its rate law, but those of an overall reaction do not? This is generally not true, the coefficients cannot be used for the reaction orders of its rate law for either type of reaction. An elementary step uses an average reaction rate calculation while the overall reaction uses an instantaneous rate calculation. Overall reactions are always in dynamic equilibrium while elementary steps are not. An elementary step is a single molecular event and occurs in one step, but the overall reaction is generally a series of elementary steps which are not necessarily proportional to the product of the overall reaction concentrations.