Do they conduct?

The idea

Ionic compounds conduct electricity in aqueous solution and in the molten state, where their ions can move freely, but not in the solid state, where the rigid structure prevents the ions from moving.

Three states

A teacher tests a solid ionic compound, its solution in water, and the molten compound with a bulb and two electrodes.

In which will the bulb light?

• In the solution and in the molten state
• Only in the solid
• In all three

Solid, solution, molten

Open every tab. These are pictures of a lab test.

Moving ions carry current

Conducting electricity through a solution needs moving charged particles. In an aqueous solution or in the molten state, the ions can move freely, so ionic compounds conduct. In the solid state the rigid structure holds the ions in place, so they do not conduct.

Ionic compounds conduct electricity in aqueous solution and in the molten state, where their ions can move freely, but not in the solid state, where the rigid structure prevents the ions from moving.

Notes

Ionic compounds conduct in solution and when molten (ions move freely), not as solids (rigid structure).

Check yourself

In which state does an ionic compound not conduct electricity?

Why does a solid ionic compound not conduct?

Why does the molten compound conduct?

In a solution of an ionic compound, the ions move to ...

• Solid — correct. Yes!
• Molten. In the molten state the ions move freely, so it conducts.
• Dissolved in water. The solution contains ions that move to opposite electrodes, so it conducts.
• It has no ions. It is made of ions; they are just not free to move.
• Its rigid structure stops the ions from moving — correct. Yes!
• It has no charge. The ions have charges; they cannot move in the rigid solid.
• Heat turns the ions into atoms. The ions remain ions; they just become free to move.
• The ions get a rigid structure. The rigid structure is in the solid; melting frees the ions.
• Heat overcomes the attraction between ions, so they move freely — correct. Yes!
• the opposite electrodes — correct. Yes!
• the same electrode. Positive ions go one way and negative ions go to the opposite electrode.
• the walls of the glass. The book says the ions move to the opposite electrodes when electricity is passed.