01Lattices
Ionic solids are 3-D arrays of alternating cations and anions. They are hard, brittle, high-melting, and conduct only when melted or dissolved (ions must move).
Brittle because shifting one layer lines up like charges, which repel and crack the crystal.
02Notebook box
Solid ionic = no conduction; molten/aqueous = conducts.
Worked example: Why doesn't solid NaCl conduct? Ions are locked in place; there are no mobile charges.