The three allotropic forms differ from one another in the arrangement of the carbon atoms in their crystals.
Diamond is one of the hardest substances known and a poor conductor of electricity.
Diamond is a gemstone. It is
also used in old phonograph needles. Heated to 1800 oC, diamond transforms
to graphite.
At room temperatures and pressures, graphite is the most stable allotrope of carbon. It is
soft, black, slippery and much less dense than diamond.
The carbon atoms
in graphite are arranged in layers, thus, giving graphite the ability to conduct electricity within the layer.
Layers easily slide over each other. As a result, graphite is used as a lubricant, as an additive
for motor oil and in pencil "lead".
This soccer-ball shaped molecule has potential applications in electronics, catalysis,
polymers, and medicines.
Carbon makes up about 0.08% of the combined lithosphere, hydrosphere, and atmosphere. It occurs in the crust
of the earth mainly in coal and petroleum and in the form of
calcium carbonate, or
magnesium carbonate rocks. Marble, limestone, chalk,
coral are found in enormous deposits throughout the world. Many of these compounds are remnants
of fossilized marine organisms.
Carbonates are used in common antacids because they react with acid such as stomach acid (hydrochloric acid, HCl).
At the same time, by similar reactions with sulfuric and nitric acids from
acid rain,
limestones which protect lakebeds are destroyed.
Carbon dioxide, of course, is essential to all life as the ultimate source of carbon in plants
and animals through its role in photosynthesis. Carbon dioxide in aqueous solution is also the
cause of acidity in natural waters. In the atmosphere, carbon dioxide can be built up from
deforestation and excessive use of fossil fuels. This may severely affect the climate through
what is known
as the "greenhouse effect".
Take a look at the research of carbon at the
Lawrence Berkeley Laboratory.
