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
Carbon has four electrons
in its valence shell (outershell). 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.
Notice
that graphite is layered.
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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 overeach 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.
 
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The 3-D coordinates
for graphite and diamond are available in the MathMol
Structural Database. We urge you to download these structures
to your home computer and use one of the suggested 3-D viewers.
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 figure shown on the left is one form composed of
60 carbons. Notice the geometric patterns of pentagons and hexagons
that form the familiar icosohedron.
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