Question

A. Explain, in terms of particles, why NaCl(s) does not conduct electricity.

Answer 1

Answer:

Ionic bonds hold charged particles in solid NaCl together, such that they are unable to move or conduct electricity.

Explanation:

Consider an electric current that flows through a conductor: charge moves in a uniform direction from one end of the conductor towards the other.

Thus, there are two conditions for a substance to conduct electricity:

• The substance shall contain charged particles, and
• These charged particles shall be free to move across the substance.

A conductor of electricity shall meet both requirements.

Now, consider the structure of solid NaCl $\rm NaCl\;(s)$. NaCl is an ionic compound. It contains an ocean of oppositely charged ions:

• Positive $\rm Na^{+}$ ions, and
• Negative $\rm Cl^{-}$ ions.

Ions carry charge. Thus, solid NaCl contains charged particles and satisfies the first condition.

Inside solid NaCl $\rm NaCl\;(s)$, electrostatic attractions ("ionic bonds") between the oppositely charged ions hold these ions in rigid ionic lattices. These ions are unable to move relative to each other. As a result, they cannot flow through the solid to conduct electricity. Under solid state, NaCl is unable to satisfy the second condition.

As a side note, melting NaCl into a liquid breaks the ionic bonds and free the ions from the lattice. Liquid NaCl is a conductor of electricity.