Ionic crystals assemble from positively and negatively charged ions. The arrangement must satisfy charge balance — the total positive charge equals the total negative charge — and each ion is pulled toward ions of opposite charge in every direction. Because the attraction is non-directional, the lattice is held by many simultaneous electrostatic interactions, and its stability scales with lattice energy, which grows as charges increase and as ions pack more closely.
How Chemical Bonds Drive Crystallisation and Crystal Growth