The follow page requires the molecular
modeling plug-in Chime which allows you to view molecules in 3-D. The molecules
can be rotated, zoomed-in/out and viewed as either wireframe, sticks, ball and
stick or space-filled models. If you need the plug-in, it's free from MDL Information
Carbon is found in many different compounds. It is in the food
you eat, the clothes you wear, the cosmetics you use and the gasoline that fuels
your car. In addition, carbon is a very special element because it plays a dominant
role in the chemistry of life. The element carbon has four electrons in its valence
shell (outer shell). Since this energy shell can hold eight electrons, each carbon
atom can share electrons with up to four different atoms. Carbon can combine with
other elements as well as with itself. This allows carbon to form many different
compounds of varying size and shape.
Carbon alone forms the familiar substances
graphite and diamond. Both are made only of carbon atoms. Graphite is very soft
and slippery. Diamond is the hardest substance known to man. If both are made
only of carbon what gives them different properties? The answer lies in the way
the carbon atoms form bonds with each other.
There are strong covalent bonds between carbon
atoms in each layer. But, only weak forces exist between layers. This allows layers
of carbon to slide over each other in graphite.
On the other hand, in diamond
each carbon atom is the same distance to each of its neighboring carbon atoms.
In this rigid network atoms cannot move. This explains why diamonds are so hard
and have such a high melting point.
The 3-D coordinates for graphite and diamond are available in
the MathMol Molecular Modeling
Database. We urge you to download these structures to your home computer
and use one of the suggested 3-D Molecular Modeling Software Packages.
Molecule of the Month Page has recently included information on diamond located
A third class of carbon compounds has recently been discovered. They
are called fullerenes. The chime model shown below is one form composed of 60
carbons. Notice the geometric patterns of pentagons and hexagons that form the
Notice the geometric patterns of pentagons and hexagons
that form the familiar icosohedron.
made of Carbon
The simplest organic compounds
contain molecules composed of carbon and hydrogen. The compound methane contains
one carbon bonded to four hydrogen's. Ethane is another example of a simple hydrocarbon.
Ethane contains two carbon atoms and four hydrogen atoms. In chemistry we use
a molecular formula to show how many atoms of each element are present in a molecule.
A molecular formula however does not show the structure of the molecule. Scientists
often use structural formulas to show the number and arrangement of atoms in a
compounds. Below the molecular formula for methane and ethane are shown. Above
the molecular formula are their respective structural formula.
Although structural formulas can be very helpful they do not give a complete
picture of a molecule. Structural formulas do not tell us anything about the distances
between bonds, the angles formed by these bonds, or the size and shape of the
molecule. Scientists use four different representation to show what molecules
THE WIRE FRAME MODEL
This model clearly shows the type
of atoms in the molecule, the distances between bonds, and angles associated with
the atoms. Because the lines drawn are very thin, molecules can very easily be
manipulated when viewed on a computer screen.
THE STICK MODEL
Atoms and bonds are represented as sticks.
THE BALL-AND-STICK MODEL
Atoms are represented by balls and bonds are
represented as sticks.
THE SPACE FILLED MODEL
This model shows the space that the molecule will take up. Because of all
the points required to draw this molecule on a computer screen you should expect
these molecules to be very difficult to manipulate.