1. (20 pts) What are the 4 most important elements on earth, in terms of its volume?  Why?
2. (10 pts) Define the electronic structures of sulfur and chromium by making spin diagrams.
3. (15 pts) Describe the expected variation in atomic radii across a given row 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) Name the type of packing associated with each illustration.

6. (25 pts) Ringwoodite, Mg₂SiO₄, is an important mineral found at depth in the upper mantle. It has the spinel structure. Determine the coordination numbers of Mg and Si, and then determine the bonding arrangement around O. (Assume the following radii, r(O) = 1.35 Å, r(Si) = 0.4 Å, r(Mg) = 0.8 Å).