How many valence electrons do insulators have?

Insulators typically have a high number of valence electrons, which contributes to their inability to conduct electricity. For materials to be classified as insulators, they usually possess five or more valence electrons. This abundance of valence electrons allows for a more filled outer electron shell, which results in a strong bond formation within the material. As a consequence, the electrons are not free to move about, thereby preventing the conduction of electrical current.

Materials such as silicon and germanium, which can have either four or more valence electrons, are semiconductors rather than complete insulators because they can conduct electricity under certain conditions, but insulators are characterized by their full outer shells leading to lack of electrical conductivity. Thus, having five or more valence electrons makes a material a strong insulator, hindering the flow of electricity compared to materials with fewer valence electrons that may generally allow for some level of conductivity.