Most molecular compounds in solid form tend to do what with electricity?

• A. They form charged ions in solution.
• B. Most molecular compounds do not conduct electricity in solid form.
• C. They always conduct electricity when dissolved in water.
• D. Most molecular compounds conduct electricity in solid form.

Answer: (B)

Electric conduction happens when there are mobile charge carriers—free ions or electrons that can move and carry charge. In solid form, most molecular compounds are made of neutral molecules held together by relatively weak forces, with electrons localized in covalent bonds and no ions roaming the lattice. Because there aren’t charged particles moving through the solid, these substances don’t conduct electricity.

If a molecular compound does dissolve in water, it may or may not ionize to form ions. Only those that produce freely moving ions in solution will conduct electricity in that state, and not all do. Likewise, conducting in the solid form is not typical for molecular compounds, whereas ionic solids can conduct when melted or dissolved because their ions become mobile.