Activated Complex refers to a compound which is highly unstable.During the chemical reaction, it has very high energy state.It acts as an intermediate product between the reactants and the products of the reaction.
The normal energy of reactant is not sufficient to start the reaction among the reactant species.This activation energy makes the collision among the reactant species effective.The activation energy of particular reaction is generally supplied by the rise in temperature.However, in photochemical reactions photon of light is (E=hv) a source of activation energy.
Energy Absorb/Release in Activated Complex
In case the energy absorbed by the activated complex is less than activation energy.Then the reaction is endothermic in nature.
If the energy release in the product is more than activation energy absorbed by the reactant.Then the reaction is exothermic in nature.
How Reaction Starts
In order to start the reaction, we supply energy.The minimum amount of energy needs to start a reaction as threshold energy.All the reactants taking part in the reaction may not have equal energy.So, extra energy needs to supply to them.We call this energy as activation energy. It is donated by Ea.
How Complex Form
The reactant the reacting species taking part in reaction do not directly change to the product.Every reactant has to cross the certain barrier of energy. This barrier is compared to the top of Hill. The reactant and product lie on the other side of Hill. The energy at the barriers is equal to the threshold energy.The reacting species in normal energy absorb the required energy of activation and reach the various at the barrier.They mutually combine to form the unstable complex compound called as activated complex.The complex being unstable changes to product by release of energy the progress of general reaction
AB + C —–→AC + B
For exothermic reaction,ΔE = -Ve (negative)
For endothermic reaction,ΔE= +Ve(positive)
This is whole about the article Activated Complex.