Which statement correctly identifies an insulator?

• A. Conducts current readily
• B. Metals like copper
• C. Elements with 1 to 3 valence electrons
• D. Materials that have 6 to 8 valence electrons and prevent current flow

Answer: (D)

An insulator resists electric current because its electrons are bound tightly and aren’t free to move, giving the material high resistance. If a material has valence electrons that are not easily excited into conduction—often associated with full or tightly bound outer shells—it tends to prevent current flow. That’s why describing an insulator as having 6 to 8 valence electrons and preventing current flow fits the concept: such electrons are generally not readily available to carry charge, so the material acts as a barrier to current.

In contrast, something that conducts current readily points to a conductor, like copper. And elements with only 1 to 3 valence electrons tend to lose electrons more readily and form conductive paths, not insulating ones.