13.4: Pauling’s Rules
- Page ID
- 18350
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In 1929, Linus Pauling summarized five general rules that apply to ionic structures. The rules, now called Pauling’s Rules, provide a convenient framework for examining some details of ionic structures (Box 13-4).
- Rule 1. Radius Ratio Principle: Cation-anion distances are equal to the sum of their effective ionic radii, and cation coordination numbers are determined by the ratio of cation to anion radii.
- Rule 2. Electrostatic Valency Principle: The strength of an ionic bond is equal to ionic charge divided by coordination number.
- Rule 3. Sharing of edges or faces by coordinating polyhedra is inherently unstable.
- Rule 4. Cations of high valence and small coordination number tend not to share anions with other cations.
- Rule 5. Principle of Parsimony: The number of different components in a crystal tends to be small.