Structure and Bonding:  Crystalline Solids

How are atoms arranged in most solids? 

View the two crystalline structures of carbon shown below.  

Diamond                                      Graphite

  

As you can see crystalline solids have a very organized arrangement of atoms (or molecules or ions).

What is the geometry of the carbon atoms in each structure?

        diamond:   ________                graphite:  ________

Right click, go to select and then mouse click action, and then select distance.  Watch the lower left of your browser screen to get the distance by clicking on two atoms.  This distance x 100 will give you picometers.  Make six measurements and record the average distance.

Measure the C-C bond length in diamond:   ________ pm

Measure the C-C bond length in the sheets of graphite:  ________ pm

Measure the C-C bond length between the layers in the graphite structure:  ________ pm

In graphite, where is the weakest force- in the layers or between the layers?  Explain.

How does the C-C bond length and hence, the bond order, compare in diamond and graphite?

In diamond, the carbon atoms are tetrahedral with sp3 hybridization, while in graphite, they are trigonal planar with sp2 hybridization.  The bonding in graphite is very similar to the behavior of benzene (see the Carbon-Carbon Bond activity).

Would the physical properties of diamond and graphite be similar or different?  Explain.

Find and compare the following physical properties of diamond and graphite:

Property Diamond Graphite
melting point    
density    
conductivity    

Are the atoms in a solid motionless?  Explain why or why not.

As you heat diamond or graphite, the crystalline structures absorb energy but do not melt.  Where does the absorbed energy go?

Look at the quartz structure  given below on the left, what is it similar to - diamond or graphite?

The small structure on the right is the repeating tetrahedral unit in the quartz structure. 

View the movies of the simulated behavior of solids from the Department of Earth Sciences at University of Cambridge.  Click below to select a movie.  These are large files so they will take a while to load.  Describe the motion of the 2-D representation of solid krypton.  

Kr (s) at 30K  Quartz  or SiO2 (s) at 300K

What intermolecular force (IMF) is holding the krypton atoms in crystalline structure?

In the quartz movie ignore the blue sodium ion that is diffusing through the quartz structure.  Describe the motion of the 3-D representation of quartz, a very common mineral such as beach sand in Ocean City, MD.

View the image of solid iodine, I2, in the space-filled display mode.  How are the molecules of iodine arranged?  You may want to change the display to ball and stick to see this better.

Is there a lot of empty space in the iodine crystal?  How about diamond or graphite?

The density of diamond is greater than graphite.  What does this imply about the packing of carbon atoms in the two crystalline structures?

The image below shows the crystalline structure of sodium chloride, NaCl.  What is the structure composed of?

How would you describe the structure?

If the temperature of a solid rises, the energy of the vibrations increases (more thermal motion in the solid) until eventually what happens to the solid? 

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