Objectives for the topic: Packing, Coordination and Sites

Reading: See syllabus

Images to understand: See syllabus

After completing this topic, the student will be able to:

1. Define the term coordination number.
2. List the typical coordination number for the following elements (in their typical valence state): Si, Al, Mn, Mg, Fe, Ca, Na, K.
3. Explain the concept of a coordination polyhedron.
4. List the coordination numbers commonly found in minerals.
5. Give the polyhedral name for coordination numbers of: 4, 6, 8.
6. Define a crystallographic site.
7. Explain the ability of different ions to be in the same type of site at different places in a crystal, and how this varies with temperature.
8. Use local charge balance diagrams to understand the bonding in minerals.
9. Describe the relative stability of corner-, edge-, and face-sharing between adjacent polyhedra, and how this varies with the charge on the cation and the coordination number.
10. Explain polyhedral distortion as described in Pauling's Rules, and what causes it.