Which type of material has 7 or 8 valence electrons typically?

The correct choice highlights that insulators typically have 7 or 8 valence electrons. This characteristic is linked to their electrical properties.

Atoms with 7 valence electrons, such as halogens, are just one electron short of achieving a stable octet configuration, which makes them highly electronegative and reactive. Atoms with 8 valence electrons, found in noble gases, have a full outer shell and thus are inert. These properties influence how materials behave; insulators do not allow electric current to flow easily because electrons are held tightly and do not move freely, preventing the conduction of electricity.

In contrast, conductors, metals, and semiconductors exhibit different behaviors based on their electron configurations. Metals, for instance, typically have 1 to 3 valence electrons, allowing them to conduct electricity by freeing up electrons that can move easily throughout the material. Semiconductors have a variable number of valence electrons, usually 4, allowing them to conduct electricity under certain conditions but not as efficiently as metals. Understanding these differences is key to grasping why insulators are characterized by their 7 or 8 valence electrons.