Geos 306, Mineralogy

Midterm, Sept 24, 2001

100 pts

1. a) (15 pts) Fill in the symbols for the first 20 elements of the periodic table.

b) (4 pts) Circle the 4 most abundant elements found in the Earth.

c) (1 pt) If these 4 elements had not included an anion, i.e., if the most abundant elements were only cations, then what type of bonding would be the most common in the Earth.

2. (10 pts) Describe the electronic structures of iron (Fe) and sulfur (S) in terms of spin diagrams.

3. (10 pts) Derive the radius-ratio rule parameter (rC/rA = .155) for a 3 coordinated cation. Draw a picture and carefully label everything so that your answer can be evaluated properly.

4. (20 pts) Enumerate the 7 types of bonding, with a short description and an example of each.

5. a) (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.

b) (10 pts) Label the packing type for each of the following diagrams.

6. Barite, BaSO 4, is an important mineral used to make paints, drilling mud, and as a solution to drink so that X-rays can be used to follow the flow of fluids in the body.

a) (12 pts) Determine the coordination numbers of Ba and S, and then determine the bonding arrangement around O. (Assume the following radii, r(O) = 1.35 , r(S) = 0.31 , r(Ba) = 1.35 ).

b) (4 pts) What are the average SO and BaO bond lengths?

c) (4 pts) Which is the stronger bond, and why?