Question

Why is the maximum number of valence electrons 8?

Answer 1

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.



The maximum number of electrons that can occupy the outermost energy level or valence shell of a Representative Element is eight (the exception is helium, which also exhibits a filled valence shell, but ony it requires only 2 electrons). As all Group VIII members have a filled valence shell, they have no tendency to react in oxidation-reduction reactions.