Ionic compounds form lattices consisting of positive and negative ions (giant ionic lattice). In an ionic lattice, the nearest neighbors of an ion are always of the opposite charge

Ionic crystals are hard but much more brittle than other types of crystal lattice.

In an ionic crystal, pushing one layer against another brings ions of the same charge next to each other. The repulsions force the layers apart

Water can also disrupt an ionic lattice. Many ionic compounds dissolve in water. Water molecules are able to interact with both positive and negative ions. When an ionic crystal dissolves, each ion becomes surrounded by water molecules. This breaks up the lattice and keeps the ions apart

Ions in solution are able to move, so the solution can carry an electric current. Ionic compounds can conduct electricity when dissolved in water

There are two other types of giant structure: giant covalent structures and giant metallic lattices.