Why do ionic compounds conduct electricity when molten or in solution?

Ionic compounds conduct electricity when molten or in solution because their ions are free to move and carry charge.

Ionic compounds are made up of positive and negative ions held together by strong electrostatic forces of attraction, known as ionic bonds. In a solid state, these ions are locked in a rigid lattice structure and cannot move freely. This is why ionic compounds do not conduct electricity in their solid state.

However, when an ionic compound is melted or dissolved in a solution, the rigid lattice structure breaks down. The ions become free to move around. This movement of ions is crucial for the conduction of electricity. Electricity is essentially a flow of charge, and in the case of ionic compounds, it is the ions that carry this charge. When an electric field is applied across a molten ionic compound or a solution of an ionic compound, the ions move towards the oppositely charged electrode, thereby conducting electricity.

For example, consider common table salt, or sodium chloride (NaCl). In its solid state, the sodium (Na+) and chloride (Cl-) ions are held together in a lattice and cannot move. But when you dissolve it in water or melt it, the Na+ and Cl- ions are free to move. If you then insert electrodes into the solution or molten salt and apply a voltage, the Na+ ions will move towards the negative electrode and the Cl- ions will move towards the positive electrode. This movement of ions constitutes an electric current, which is why we say that the solution or molten salt conducts electricity.

In summary, the ability of ionic compounds to conduct electricity when molten or in solution is due to the mobility of their ions, which can carry charge under the influence of an electric field.