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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 Systems.
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.
The Molecule of the Month Page has recently included information
on diamond located here
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 familiar icosohedron.
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Fullerene
Notice the geometric patterns of pentagons and hexagons
that form the familiar icosohedron.
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Compounds
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
look like.
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.
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