Geos 306, Mineralogy
Midterm, Sept 20, 2000
100 pts

1. (20 pts) What are the 4 most important elements on earth, in terms of its volume?  Why?
2. (10 pts) Describe the electronic structures of magnesium (Mg) and germanium (Ge) in terms of spin diagrams.
3. (10 pts) Describe the expected variation in atomic radii down a given column of the periodic table. Why?
4. (20 pts) Enumerate the 7 types of bonding, with a short description and an example of each.
5. (10 pts) Suppose the illustrated figures represent closest-packed arrangements of anions. Identify the different locations where cations could be coordinated with 2, 3, 4, 6, or 12 anions. In the position of the cation, write its coordination number.

6. (20 pts) Zircon, ZrSiO4, is an important mineral used in dating metamorphic rocks. It is also the most incompressible silicate mineral known.
(a) Determine the coordination numbers of Zr and Si, and then determine the bonding arrangement around O. (Assume the following radii,  r(O) = 1.23 Å, r(Si) = 0.37 Å, r(Zr) = 0.97 Å).
(b) What are the average SiO and ZrO bond lengths?
(c) Which is the stronger bond, and why?
7. (10 pts) Enumerate the 6 crystal systems and their constraints on the cell parameters.