The term, which describes the unstable arrangement of the reacting particles as a chemical reaction takes place is ACTIVATED COMPLEX.
Activated complex is a point along the reaction path in which the reacting particles have the highest energy and the highest instability. Activated complex is a phase which all chemical reactants have to pass through before they become products. The phase is a temporary phase because of its instability. An activated complex will form products if it has enough energy to do so, otherwise, the activated complex break apart and revert to reactants.
