Define the relationship between the elementary steps of a mechanism and the net reaction. Define an intermediate and a transition state. Transition State- extremely short lived species which shows the breaking and forming of bonds. It is also called the activated complex. It is the species of highest energy state in every elementary step.
Every elementary step has a transition state.
Not all elementary steps have an intermediate. There is no intermediate but does have a transition state. Such mechanisms would have a transition state for each elementary step. There may or may not be an intermediate for each elementary step. Rate law for a multi-stepped reaction where the initial step is a fast equilibrium.