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Why is Graphite soft and Diamond hard if both are pure carbon?
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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.
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[Graphite structure shown using the Jmol
Applet]
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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.
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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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[Diamond structure shown using the Jmol
Applet]
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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?
