Activation Energy

ACTIVATION ENERGY

The first and most important fact about any chemical reaction or any elementary step in a chemical process is that there is an energy barrier separating the products from the reactants (Figure 5.1). For the reactants to be converted to products, the energy of the system must be raised until the energy of the reactant(s) is equal to the height of energy barrier. 

Then and only then can the reactants change into products by passing over the barrier and relaxing into the product state. The energy barrier is of prime importance because (a) the height of the barrier determines how fast reactants can be converted to products at a given temperature and (b) at the maximum height of the energy barrier, which is called the transition state, there is a collection of atoms, called the activated complex, that is the structural bridge between reactants and products.