Which statement best describes conductivity for metallic, ionic, and covalent bonds in solids and liquids?

• A. Metals conduct electricity only in the solid state.
• B. Metals conduct in both solid and liquid; ionic compounds conduct only when molten or dissolved; covalent solids are insulators.
• C. Ionic solids conduct electricity in the solid state; metals do not conduct.
• D. Covalent solids conduct electricity in all states.

Answer: (B)

The key idea is how charge carriers move in different bonding types. Metals have a sea of delocalized electrons that are not tied to any one nucleus, so those electrons can flow when a potential is applied. That freedom exists in both solid metals and molten metals, so metals conduct in both states.

Ionic compounds rely on ions to carry charge. In a solid ionic lattice, ions are locked in place, so there’s no continuous path for electricity. When melted or dissolved, the ions become mobile, and conductivity appears.

Covalent solids, on the other hand, form strong bonds between atoms with little to no free charge carriers moving around, so they behave as insulators. An exception you might have seen is graphite, where layers allow some conduction along the planes, but that’s a special case outside the general behavior of covalent solids.

So the statement that metals conduct in both solid and liquid, ionic compounds conduct only when molten or dissolved, and covalent solids are insulators best describes the typical conductivities in these states.