Science glossary film: Reactivity

The tendency of a substance to undergo chemical reactions. The reactivity of elements is related to the number and arrangement of electrons in their atoms. Atoms need a full outer shell of electrons to be stable. So atoms with only one or two outer electrons, or that are only lacking one or two electrons, tend to lose or gain these electrons readily, and so are highly reactive.

The reactivity of elements is related to the number and arrangement of electrons in their atoms. Atoms need a full outer shell of electrons to be stable. So atoms with only one or two outer electrons, or that are only lacking one or two electrons, tend to lose or gain these electrons readily, and so are highly reactive.