Name:

Section:

1. The appropriate sections of your textbook.

1. Give 4 examples of crystals which you encounter on (almost) a daily basis.
2. Consider the parallelogram defined by the centers of 3 rows of close-packed spheres, 5 spheres per row, shown in a below.
   1. Calculate the parallelogram area in terms of sphere radius.
   2. Show that the area is smaller than that covered by the centers of spheres arranged as shown in b above.