How many valence electrons does an insulator generally have?

The correct choice reflects that insulators typically have 7 or 8 valence electrons. Insulators are materials that do not conduct electricity well because their valence electrons are tightly bound to their atoms and do not move freely.

Elements in the group of the periodic table that have 7 or 8 valence electrons include nonmetals such as noble gases and halogens. For instance, elements like neon and argon, which have 8 valence electrons, are excellent insulators, while chlorine and fluorine, having 7 valence electrons, can also exhibit insulating properties but tend to be more reactive.

This configuration of having a complete set of valence electrons (especially 8, known as the octet rule) means that these materials are stable and do not easily lose electrons to become conductive. Thus, the presence of 7 or 8 valence electrons sets the foundation for insulative behavior in these materials.