Today I continued talking about coordination, and I discussed Pauling's rules. THESE ARE IMPORTANT (both coordination and Pauling's rules). I also talked about basic features of crystal structure types from a crystal chemistry point of view.

Be sure to read the relevant sections of Chapter 3 and the beginning sections of Ch. 4 in the textbook. I will not quiz you on material in the text that I do not discuss in class, so although I encourage you to read the entire chapter (3), you should focus in particular on understanding the sections that relate to class discussions.

What is packing?

What are the two possible closest packed structures for 3-dimensional arrangements of equal-sized spheres?

What are the most common coordination numbers in minerals? (know what geometrical arrangement corresponds to each coordination number)

What are Pauling's rules? (don't list them, just describe in general what they represent)

How can the radius ratio of a cation-anion pair be used to calculate coordination number?

What do the following terms mean: isodesmic, anisodesmic, mesodesmic?

What is the significance of silicates being mesodesmic?

What common mineral group is anisodesmic? What is a common isodesmic mineral?

Why do coordinating tetrahedra seldom share edges and, even more rarely, faces?

question to think about over the weekend: under what geological circumstances might a mineral be stable with face-sharing polyhedra such as Al-O octahedra)?