Final answer:
A transition state or activated complex is a temporary, high-energy state in a chemical reaction where reactant bonds are partially broken and product bonds are starting to form.
Step-by-step explanation:
A transition state, also known as an activated complex, is an arrangement of atoms that represents a temporary condition during a chemical reaction. This unstable combination of reactant species is formed when molecules have successfully overcome the activation energy, allowing a chemical reaction to proceed.
At this peak of the potential energy curve, the activated complex exists. It is a high-energy state, and because of this, it is short-lived, lasting only about 10-13 seconds.
In the transition state, reactant bonds are partially broken and product bonds are partially formed. The transition state can either revert to the reactants or proceed to form the products, depending on subsequent molecular interactions.
The concept of an activated complex is crucial when discussing reaction mechanisms and energy profiles, as the energy required to achieve the transition state is directly linked to the reaction rate and the activation energy.