Why does sodium chloride not conduct electricity as a solid but when melted, does conduct electricity?

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Solid NaCl consists of a three dimensional array of Na^+ and Cl^-. Even though the ions are present, the ions are not free to move about; i.e., they are held in place by crystal lattice forces that make up the solid. They CAN vibrate, and do, but they are not free to move from one spot to another and that is necessary for electrical conduction to take place. When NaCl melts, however, the crystal lattice is broken down (energy is supplied by the heating device used--bunsen burner or hot plate) and in liquid form the ions ARE free to move from one place to another. Therefore, the ions can conduct electical current from one electrode to another. I hope this is clear to you.

To understand why sodium chloride (NaCl) does not conduct electricity as a solid but conducts when melted, let's break it down step by step:

1. In a solid state: Solid NaCl consists of positively charged sodium ions (Na+) and negatively charged chloride ions (Cl-) arranged in a three-dimensional crystal lattice structure. The ions are not free to move as they are held in place by strong electrostatic forces from the surrounding ions. These forces keep the ions constrained in fixed positions, and they are not able to move and carry electric charge.

2. Electrical conduction: In order for a substance to conduct electricity, there must be charged particles that are free to move. In the solid state, as mentioned earlier, the ions in NaCl are not free to move, so it cannot conduct electricity.

3. Melting process: When heat energy is supplied to NaCl, it gains enough thermal energy to overcome the electrostatic forces holding the ions in place. As a result, the crystal lattice structure breaks down, and NaCl melts into a liquid state.

4. In a liquid state: In the liquid state, the positively charged sodium ions and negatively charged chloride ions are now free to move. The thermal energy allows the ions to overcome the attractive forces and move randomly throughout the liquid. Since the charged particles can move, they can carry electric charge and conduct electricity.

In summary, NaCl does not conduct electricity as a solid because the ions are held in place by strong attractive forces in the crystal lattice. However, when melted into a liquid state, the crystal lattice breaks down, and the ions become free to move, allowing the substance to conduct electricity.