What is elementary reaction?

An elementary reaction is a chemical reaction that occurs in a single step or a series of simple consecutive steps, involving the collision and transformation of reactant molecules into product molecules. These reactions follow the principle of microscopic reversibility, meaning that the products can also undergo the reverse reaction to reform the original reactants.

Elementary reactions are characterized by their rate law, which can be determined experimentally and based on the stoichiometry of the reaction. The rate of an elementary reaction is typically proportional to the concentration of the reactants raised to the power of their respective stoichiometric coefficients.

Elementary reactions play a crucial role in chemical kinetics as they serve as the building blocks for more complex chemical reactions. Understanding elementary reactions is essential for predicting reaction pathways, determining reaction mechanisms, and optimizing reaction conditions in various chemical processes.

Examples of elementary reactions include unimolecular reactions, bimolecular reactions, and termolecular reactions. Unimolecular reactions involve the decomposition or rearrangement of a single molecule, while bimolecular reactions involve the collision and reaction of two molecules. Termolecular reactions involve the collision and reaction of three molecules, although they are relatively rare due to the lower probability of three molecules colliding simultaneously with the correct orientation and energy.