Pauling's rules apply to ionic crystals and describe the way in which the structure of
ionic crystals is organised such that it minimizes potential energy.
- A coordination polyhedron of anions is formed about each cation,
the cation-anion distance essentially
equaling the sum of their characteristic packing radii and their radius
ratio determining both the nature of the coordination polyhedron and therefore
the coordination number of the cation.
- An ionic structure will be stable to the extent that the sum of
the strengths of teh electrostatic bonds that reach an anion from
adjacent cations equals the charge on the anion
- the sharing of edges and particularly the faces by two anion
polyhedra decreases the stability of an ionic crystal structure.
- In a crystal structure containing different cations, those
of high valency and small coordination number tend not to share polyhedron elements with each other
- The number of essentially different kinds of
constituents in a crystal tends to be small.