Metal and Alloys

Why does magnesium oxide conduct electricity when molten?


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Magnesium oxide is an ionic substance, so when in a solid state the ions are held in a strong lattice formation (electrostatic forces of attraction between oppositely charged ions). Ionic substances can only conduct electricity if their ions are free to move. In a molten state, the ions become free to move (the strong electrostatic forces of attraction are overcome when the melting poing is reached) and can therefore carry a charge (i.e. conduct electricity).