In these expressions, A, B, and n are constants whose values depend on the particular
ionic system. The value of n is approximately 8.
Ionic bonding is termed nondirectional; that is, the magnitude of the bond is equal
in all directions around an ion. It follows that for ionic materials to be stable, all
positive ions must have as nearest neighbors negatively charged ions in a threedimensional
scheme, and vice versa.The predominant bonding in ceramic materials is
ionic. Some of the ion arrangements for these materials are discussed in Chapter 12.
Bonding energies, which generally range between 600 and 1500 kJ/mol (3 and
8 eV/atom), are relatively large, as reflected in high melting temperatures.4 Table
2.3 contains bonding energies and melting temperatures for several ionic materials.