Definition: Reactivity refers to the ability of a substance or system to undergo a chemical reaction with other substances or systems.

Key Concepts

  • Chemical reaction: A process in which one or more substances are converted into different substances, often accompanied by the release or absorption of energy.
  • Substance: Any matter that has a definite composition and distinct properties.
  • System: A set of interrelated components or processes that interact with each other.


1. Affinity: Reactivity is influenced by the affinity of a substance towards other substances. Higher affinity generally leads to a higher reactivity.

2. Reaction rate: Reactivity is often associated with the speed at which a chemical reaction occurs. Faster reactions are considered more reactive.

3. Reactivity series: Elements and compounds can be arranged in a reactivity series based on their relative reactivity. This series helps predict the outcome of reactions.

Factors Affecting Reactivity

1. Nature of the substance: Different substances exhibit varying degrees of reactivity based on their atomic or molecular structure.

2. Temperature: Higher temperatures generally increase the rate of reactions and consequently the reactivity.

3. Concentration: Higher concentrations of substances often lead to greater reactivity due to increased collision frequency.

4. Presence of catalysts: Catalysts can significantly enhance the reactivity of a substance by lowering the activation energy required for a reaction.


Understanding reactivity is essential in various fields, including:

  • Chemistry: Reactivity helps in predicting and controlling chemical reactions, aiding in the design of new molecules and materials.
  • Environmental science: Assessing the reactivity of substances is crucial in understanding their impact on ecosystems, pollution, and atmospheric chemistry.
  • Pharmaceuticals: Reactivity plays a vital role in drug development, ensuring desired interactions and minimizing harmful side effects.