Focus question

What are some characteristics of the carbon-60 (buckyball) molecule?

Essential materials

• Two copies of Pattern 1 and one copy of Pattern 2 printed on stiff paper
• Pair of scissors
• Cellophane tape
• Optional: felt tip marker and ruler

Main ideas and background information

• The carbon-60 (C₆₀) molecule is a form of carbon that was discovered relatively recently (1985). It has the shape of a truncated icosahedron, one of a number of geometrical solids, with a carbon atom at each of its 60 vertices. This molecule has the same general geometrical properties as a football, or a soccer ball if you are in the USA.
• This molecule and others with a similar geometrical makeup of carbon atoms are called fullerenes. They are named after Buckminster Fuller, an accomplished engineer and inventor. Fuller developed designs for many innovations, including the geodesic dome. The C₆₀ molecule is often called a buckyball because of its uncanny resemblance to Fuller’s geodesic structure.
• The other forms of carbon are diamond and graphite, both of which have been well known for some time.
• Each carbon atom has four electrons in its outer shell. These electrons are available for sharing with other atoms. When two atoms share electrons in their outer shells, a molecular bond is created between the two atoms.
• For a stable configuration, a carbon atom must have all four outer electrons bonded. In the buckyball model, the edges (lines between the carbon atoms) represent the bonds. A carbon atom at any vertex has only three apparent bonds, represented by the three edges that come together. Notice that, for any vertex, two of the three edges are part of a pentagon, while the third edge is between two hexagons.
• The two edges along the pentagon are single bonds. Each single bond involves one of the four outer electrons from each of the two bonding atoms. The edge between hexagons represents a double bond that involves two of the outer electrons in each of the two bonding atoms. The two single bonds and the one double bond involve all four outer electrons in each carbon atom, giving the buckyball a stable configuration.
• Each edge (carbon-carbon bond) of a buckyball has a length of about 0.14 nanometers (nm). One nanometer is equal to one ten-millionth of a centimeter, or 0.0000001 cm. A regular sheet of paper is about 100,000 nm thick, or the length of more than 700,000 buckyballs in a line.
• The general fullerene structure of carbon includes many other molecular arrangements than just the buckyball. These arrangements are quite strong and adaptable. They can form the basis of a material that is lighter and stronger than steel. In the future, the C₆₀ molecule might be used as a “cage” for the transportation and protection of molecules of other substances. For more information, click on Digging Deeper.
• The discovery of fullerenes is part of a movement toward nanotechnology, the study and exploitation of particles in the 1 to 100 nm range. Many exciting future applications are being explored.

Procedural tips

• Suggestion: Before cutting out the patterns, draw a dot with a marker at each vertex of all hexagons to indicate the location of carbon atoms. When the buckyball is assembled, the dots will show clearly the geometrical structure of the atomic arrangement.
• Before taping sections of hexagons together in Steps 2 and 5, fold and crease the stiff paper along the line between adjacent hexagons. This will give your final solid its angular form.
• As you tape the various sections together, be sure to fold and crease the taped joint as well.
• Suggestion: After the buckyball is assembled, draw a heavy line along the crease between all pairs of hexagons. These lines represent the double bonds. Do not draw along the lines that create the pentagons. Each hexagon should end up with single bonds and double bonds alternating around its perimeter, for a total of three single and three double bonds.

Discussion

1. Carbon atoms in the buckyball are arranged into five- or six-atom rings. How many of each ring are there?
   Answer: There are 12 five-atom rings (pentagons) and 20 six-atom rings (hexagons).

2. How are the five- and six-atom rings alike and how are they different?
   Answer: The two types of rings are alike because each ring is formed by carbon atoms. They are different because of the different number of carbon atoms in each. They also have different neighbors. Each five-atom ring (pentagon) has five six-atom rings as neighbors, but it does not share a boundary with any other five-atom ring. Each six-atom ring (hexagon) has three five-atom rings and three six-atom rings alternating as neighbors. (In some science books, the five-atom rings are called isolated and the six-atom rings are called contiguous, meaning that each six-atom ring shares a boundary with another six-atom ring).

3. How many single bonds and how many double bonds does each carbon atom in the buckyball have?
   Answer: Each carbon atom has two single bonds, represented by the edges along the pentagons, and one double bond, represented by the edges between hexagons.

4. How many single bonds and how many double bonds does the buckyball have in total?
   Answer: Students can count the 60 single bonds and 30 double bonds. However, encourage them to calculate these numbers, knowing that there are 60 carbon atoms, each with two single bonds and one double bond. Each bond involves two atoms, so each atom contributes half of two single bonds and half of one double bond.

5. If each bond is about 0.14 nm long, what is the approximate diameter of a buckyball?
   Answer: This can be estimated to be about 0.7 nm. Also see Edinformatics.com for an online resource with a “virtual” buckyball that students can measure in angstroms to confirm their estimates. One nanometer equals 10 angstroms.

6. What is in the middle of a buckyball?
   Answer: Nothing! The buckyball is a hollow molecule. This is one of the characteristics that makes it so exciting to scientists. They are trying to find ways to use this “cage” as a container for molecules in many applications.

7. How might this activity relate to everyday life?
   Answer: For the future, buckyballs and other fullerenes will help us develop many nanotechnology applications. For the present, whenever you see a football or American soccer ball, think of the buckyball!

Assessment

Are students able to describe some characteristics of the carbon-60 (buckyball) molecule?

Answer: The buckyball is a hollow molecule consisting of 60 carbon atoms arranged in the shape of a football or American soccer ball (truncated icosahedron). It has 12 isolated five-atom rings and 20 contiguous six-atom rings. There are 60 single bonds and 30 double bonds in each C-60 molecule. The diameter of a buckyball is about 0.7 nm. It is classified as a fullerene, a relatively new form of carbon.

Extensions and further investigations

• Have students
  – construct buckyball models of different sizes and investigate their properties. Use a photocopier to enlarge or reduce the patterns. Alternatively, challenge students to use protractors and rulers to construct their own enlargements.
  – create molecular scale models of common substances such as water to determine if they will fit inside a buckyball.
  – research the similarities and the differences between a buckyball and a geodesic dome.

• Before the students carry out each additional activity, challenge them to predict what they think will happen and why. Then have them compare the results with their predictions and develop possible explanations for any discrepancies.

Career connections

• Nanotechnology engineering
• Physics
• Materials science

Correlations with Standards

United States: This activity correlates with portions of NSES Content Standard A, Science as Inquiry, and Content Standard G, History and Nature of Science, Grades 5-8 and 9-12, and with the following additional standards:

Grades 5-8
Standard B - Physical Science: B1

Grades 9-12
Standard B - Physical Science: B2

Britain: This activity correlates with the English National Curriculum standard Sc1, Science Enquiry, and the following additional standards:

KS4, extension work only; KS5, chemistry

Glossary/vocabulary

truncated icosahedron
fullerene
buckyball
bond
nanometer
nanotechnology
isolated
contiguous

Resource links

Sites with additional information about fullerenes and nanotechnology:

Fullerene Science Module
Washington University

Nanotubes and Buckyballs
Nanotechnology Now

Center for Nanoscale Science and Technology
Rice University

National Nanotechnology Initiative

Companies that sell kits for students to build buckyballs and other fullerenes:

Cochranes of Oxford Ltd.

Zometool, Inc.

Indigo® Instruments

Sites with geodesic dome information:

The Buckminster Fuller Institute

Thirteen Online

Wikipedia