Sodium chloride (NaCl), commonly known as table salt, is an insulator in its solid state but a conductor when dissolved in water or melted. Here's why:

Solid State:

* Ionic Bonding: Sodium chloride is an ionic compound, meaning it forms a crystal lattice where positively charged sodium ions (Na+) and negatively charged chloride ions (Cl-) are held together by electrostatic forces.

* Fixed Ions: In the solid state, these ions are locked in their positions within the lattice. They cannot move freely.

* No Free Charge Carriers: Since the ions cannot move, there are no free charge carriers to conduct electricity. Therefore, solid NaCl is an insulator.

Dissolved in Water or Melted:

* Ion Mobility: When sodium chloride dissolves in water, the ions dissociate (separate) and become surrounded by water molecules. These dissolved ions can now move freely.

* Charge Carriers: The mobile ions in the solution act as charge carriers, allowing electricity to flow through the solution.

* Conductivity: Therefore, dissolved sodium chloride is a good conductor of electricity. Similarly, melted NaCl conducts electricity because the ions can move freely in the molten state.

In summary: The ability of sodium chloride to conduct electricity depends on the freedom of movement of its ions. In solid form, the ions are fixed and cannot move, making it an insulator. In dissolved or molten form, the ions are free to move, making it a conductor.