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Explore the fundamental principles of ionic bonding, coordination arrays, coordination numbers, and radius ratio computation. Learn how anions and cations cluster based on electrostatic attraction and the common configurations in coordination chemistry. Discover the significance of fitting, coordination numbers, and the Radius Ratio concept in predicting stable arrangements.
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Coordination Principle GLY 4200 Fall, 2012
Electrostatic Attraction • Anions and cations cluster together because they are attracted electrostatically • The clusters form coordination arrays
Ionic Bonding • The coordinated ions always cluster about the coordinating ion in such a way that their centers lie at the apices of a polyhedron • For bonding that is non-ionic, the same general principles hold
Coordination Number • The number of coordinated ions around a central ion is known as the coordination number (CN)
Radius Ratio • The radius ratio is the ratio of the cation (note: this is Rc) to the anion (Ra) or (R+/R-) • Since anions are almost always larger than cations, the ratio is between zero and one
Fit • Perfect • Cation large, pushes anions apart • Cation small, rattles around (unstable)
