Final answer:
Ionic compounds are unique in that they conduct electricity when dissolved in water or molten, but not in solid form due to the mobility of ions in these states. The strong ionic bonds in solid ionic compounds prevent ion movement, making them non-conductive; once melted or dissolved, these compounds can conduct electricity.
Step-by-step explanation:
What is unique about ionic compounds in the idea of conductivity is that they can conduct electricity when they are either dissolved in water or melted into a liquid state, but not when they are in solid form. In a solid state, the ions in ionic compounds are held in a fixed crystalline structure by strong ionic bonds and cannot move freely, making the compound non-conductive. However, when ionic compounds dissolve in water or are melted, the ions are free to move, allowing them to conduct electricity.
Solid ionic compounds are poor conductors of electricity due to the strength of ionic bonds that keep ions from moving freely. But when ionic compounds dissolve in water or become molten, these formations break down, the ions become mobile, and as a result, ionic solutions or melts are excellent conductors as the ions can carry electrical charges from one place to another.
For example, sodium chloride, a common ionic compound, exhibits this property. It melts at 801 °C and boils at 1413 °C. In solid form, it does not conduct electricity, but in a molten state or dissolved in water, it can conduct electricity because the ions are able to move freely.