The molecularity of a chemical reaction refers to the number of molecules or chemical entities that participate as reactants in the elementary reaction step leading to the formation of products. It is determined by examining the reaction mechanism and identifying the number of molecules directly involved in a single step. Molecularity classifications include unimolecular (involving one molecule), bimolecular (involving two molecules), and termolecular (involving three molecules). Molecularity is a crucial aspect in reaction kinetics, influencing the rate equation and providing insights into the reaction’s overall complexity and mechanism. Understanding molecularity aids in predicting and studying the kinetics of chemical reactions.