Definitions:

1. An electron in the outer shell of an atom which can combine with other atoms to form molecules. NOUN
   • The number of valence elctrons determines an atom's chemical properties and reactivity.
2. An electron in the outermost shell or energy level of an atom that is involved in forming chemical bonds with other atoms. NOUN
   • Sodium has one valence electron, which it readily loses to form a positive ion.

Synonyms:

• chemical bonding
• electron shell
• octet rule