Listen to the full series on BBC Sounds. Ionic compounds have high melting and boiling points, so they are in the solid state at room temperature. See the study guide on the three states of matter ...

a single grain of salt may contain 1.2 × 10 18 (1,200,000,000,000,000,000) ions. The lattice arrangement continues in three dimensions. This is why solid ionic compounds form crystals with ...