Question

what is the most likely reason that nonmetals are electrical insulators?
since valence shells are mostly empty in nonmetal atoms, the atoms attract and hold any electrons they can in order to fill their valence shells.
since valence shells in nonmetal atoms are almost full, the atoms attract electrons and hold them tightly to fill their valence shells.
since all nonmetals have valence shells that are full, they hold electrons tightly to avoid changing.
since all nonmetals have valence shells that are completely empty, they do not attract or release any electrons.

Explanation:

To determine the correct answer, we analyze the electron configuration of nonmetals and their electrical conductivity:

1. Option 1: Nonmetal valence shells are not "mostly empty"—metals typically have empty or nearly empty valence shells (allowing free electrons). Nonmetals have valence shells that are nearly full, so this is incorrect.
2. Option 2: Nonmetal atoms have valence shells that are almost full (e.g., 5–7 valence electrons for most nonmetals). To fill their shells (achieve stability), they attract electrons and hold them tightly. Tightly held electrons cannot move freely, so nonmetals cannot conduct electricity (they are insulators). This matches the properties of nonmetals.
3. Option 3: Not all nonmetals have full valence shells (e.g., oxygen has 6, nitrogen has 5). Only noble gases have full valence shells, so this is incorrect.
4. Option 4: Nonmetal valence shells are not "completely empty"—empty valence shells are characteristic of metals (e.g., alkali metals have 1 valence electron, so their outer shell is mostly empty). Nonmetals have nearly full shells, so this is incorrect.

Answer:

B. Since valence shells in nonmetal atoms are almost full, the atoms attract electrons and hold them tightly to fill their valence shells.