the electrons found in the outermost energy level of an atom
Valence electrons are defined as electrons that are found in the outermost energy levels of an atom. The number of valence electrons in any atom of a Representative Element corresponds to its Group Number. All elements within a Group or Family, have the same number of electrons in their outermost energy levels. This outermost energy level is referred to as an element's valence shell, as sketched below.