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Why
is Graphite soft and Diamond hard if both are pure carbon?
Carbon
alone forms the familiar substances graphite and diamond. Both graphite and diamond
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.
| [Graphite
structure shown using the JMol Applet] | Try
this:
Rotate the Graphite molecule (Hold
the left mouse button down over the image and move the mouse to rotate the graphite
molecule). Notice
that graphite is layered. While
there are strong covalent bonds between carbon atoms in each layer, there are
only weak forces 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.
| [Diamond
structure shown using the JMol Applet] | Try
this!! Rotate
the structure of diamond -- Notice
that each diamond atom is the same distance to each of its neighboring carbon
atoms. There is a rigid network of bonds within the diamond crystal. What
is the bond length for a diamond C-C bond? | | |
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1) What is the
distance of the CC bond in diamond?
Please enter
your answer in the space provided:
2) What is the distance of the CC bond in graphite?
3)What is distance between the graphite
layers?
