9.1 Ionic radius ratio & coordination polyhedra of ions 9.2 The crystal structures of some 9.3 Lattice energy 9.4 Ionic radii 9.4.1 How to determine ionic radii 9.4.2 Effective ionic radii 9.4.3. The trend of variation of ionic radii 9.4.3 Polarization of ions 9.5 The Pauling rule of Coordination polyhedra for ionic crystals 9.6 Structural chemistry of silicates