Homework #3
Lecture 4
Name _____________________
Use this to review Lecture 4. Turn in the answer sheet next class.
1. A cation is touched by 6 anions. What is the coordination number of the
cation?
a. 6
b. 8
2. In the above situation, the anions are arranged in a(n)
a. octahedron
b. tetrahedron.
3. Consider the mineral halite, NaCl , aka “salt”. Na+ is found to have a
radius of 0.95 angstroms, and Clz has a radius of 1.81 angstroms.
Calculate the radius ratio.
a. 0.525
b. 1.91
4. For Halite, what coordination number do you expect the Na+ to have, i.e.,
how many Chloride Cl- ions are touching it? (Page 72)
a. 6
b. 8
5. What coordination number is a body-centered cube BCC?
a. 12
b. 8
6. In pure zinc Sphalerite, ZnS, Zinc ion Zn++ has a radius of 0.60
angstroms, and Sulfide ion S—has a radius of 1.84 Angstroms. What
packing geometry do you expect? (Page 72 and 85)
a. tetragonal (C.N. = 4)
b. octagonal (C.N. = 6)
7. Calculate the electrostatic valency for Sphalerite (Pauling’s Rule 2)
a. 0.5
b. 1.0
Geology 3261 Homework 3
ANSWER SHEET
Name: __________________________
Homework assignments may be discussed with classmates
Circle your answer:
1.
a or
b
2.
a or
b
3.
a or b
4.
a or b
5.
a or
b
6.
a or
b
7.
a or
b