Chemistry - Electrochemistry Question with Solution | TestHub

Diamond is a covalent network solid where all valence electrons of carbon are involved in bonding, leaving no free electrons to conduct electricity.

Solid sulphur is a molecular solid with no free electrons or ions, so it acts as an insulator.

Crystalline NaCl is an ionic solid where the ions are held tightly in a rigid lattice and cannot move, so it does not conduct electricity.

In molten NaCl, the electrostatic forces of attraction between the oppositely charged ions are overcome by heat. The ions become free to move and can conduct electricity.

Answer: Molten NaCl