Reactivity (chemistry)

Reactivity is a measure of how much a substance tends to react with other things. Some substances are more reactive, and others are less reactive. Reactivity is set by several factors:
Reactivity involves both the thermodynamics and kinetics of the particular chemical reaction. A reaction will be more reactive if the total energy of the products is less than the total energy of the reactants. A reaction will be more reactive if the energy of its transition is low.
Lithium reacts with water and air. Gold does not react with water or air. Gold is unreactive, thus low on the reactivity series. Lithium is reactive. There are several ways to measure reactivity. Some are reducing agents, and others can be oxidizing agents. Some absorb water easily. Some break down easily.