Final answer:
Insulators generally have 5 to 8 valence electrons, with the best answer being C) 7-8. This full or nearly full valence shell configuration makes it difficult for such materials to conduct electricity. For example, nitrogen has two electron shells and does not conduct electricity well.
Step-by-step explanation:
Insulators generally have valence electrons in the range of 5 to 8. These electrons are in the outermost shell of an atom and determine its ability to conduct electricity. Insulating materials, such as rubber and glass, often have a complete valence shell with 8 electrons (or a filled valence shell with 5 and 6 electrons due to a stable electron configuration), making it difficult for them to conduct electricity because they hold their electrons tightly and do not allow the free flow of electrons.
Based on the options provided in your question, the most accurate answer would be C) 7-8 for insulators. This is because atoms with a nearly complete or complete valence shell tend not to allow electrons to move freely, hence they do not conduct electricity well and serve as insulators.
As an example, nitrogen (with an atomic number of 7) likely has two electron shells, and with 5 electrons in its valence shell, it is more of a non-metal and does not conduct electricity well, reflecting the characteristics of insulators with respect to their valence electrons.