CHE 423 Inorganic Chemistry Laboratory

Experiment #4: Solid State Structure and Properties

Name__________________ Partner_______________

Purpose

In this lab, you and your partner will build structural models for solid state compounds and explore the properties of some of these substances. By building the models, you will get practice looking at these three dimensional structures. You will also see how bulk properties arise from the atomic scale ordering in the solid state.

Procedure

Each team of two will get two model kits. Using these kits, you will build one structure while your partner builds the other structure in each pair of compounds. Once you've built the models, compare and contrast the two structures, fill in the data sheet and answer the specific questions for each pair. For some substances, you will need to perform mini-experiments on the materials in order to answer the questions. Finally, choose one structure from the list and build more than one unit cell of it. Draw the unit cell and find the symmetry elements that are present in the cell.

Structure pairs

1) A. Primitive Cubic

B. Body-Centered Cubic

2) A. CsCl (first layer Cs)

B. CsCl (first layer Cl)

3) A. Hexagonal close-packing

B. Cubic close-packing

4) A. Rock salt (NaCl)

B. Rock salt (NaCl body diagonal)

5) A. Diamond

B. Graphite (borrow 4 colorless spheres from partner)

6) A. Face-centered cubic

B. Face-centered cubic (body diagonal)

Data Sheet

	1A	1B	2A	2B
What color is a LARGE sphere?
How many large spheres at:
corners
faces
edges
inside
total in cell?
How many nearest neighbors:
below
same layer
above?
What is the coordination number?
What color is a SMALL sphere?
How many small spheres at:
corners
faces
edges
inside
total in cell?
How many nearest neighbors:
below
same layer
above?
What is the coordination number?
What is the formula for the unit cell?
Is the structure close-packed?
If so, ABA or ABCA?

Specific comparisons:

1) Which structure is more efficient at filling space? How would the density of the same element in either of these packing structures compare?

2) What is the lattice-type of just the large spheres? Of just the small spheres? What is the difference, if any, between the two structures? Which unit cell is correct?

	3A	3B	4A	4B
What color is a LARGE sphere?
How many large spheres at:
corners
faces
edges
inside
total in cell?
How many nearest neighbors:
below
same layer
above?
What is the coordination number?
What color is a SMALL sphere?
How many small spheres at:
corners
faces
edges
inside
total in cell?
How many nearest neighbors:
below
same layer
above?
What is the coordination number?
What is the formula for the unit cell?
Is the structure close-packed?
If so, ABA or ABCA?

3) What is the difference, if any, between the two structures? How do the packing efficiences qualitatively compare to those of the primitive cubic and body-centered cubic structures?

Mini-experiment: bend a piece of copper wire. Does it break? Explain by referring to the cubic close-packed structure, which is the structure of copper. For example, lift one of the bottom corner spheres in the model and describe what happens.

4) What is the structure of just the large spheres? Of just the small spheres?

Mini-experiment: Use the edge of a spatula to break a crystal of rock salt. How does it break? Which plane in the model do you think corresponds to the cleavage plane?

	5A	5B	6A	6B
What color is a LARGE sphere?
How many large spheres at:
corners
faces
edges
inside
total in cell?
How many nearest neighbors:
below
same layer
above?
What is the coordination number?