The element carbon is a non-metallic material that contains six electrons. Charcoal, a form of carbon, has been used since prehistoric times. The name carbon comes from the Latin word carbo which means charcoal. Carbon can be found in organic material such as plants and animals, and in inorganic materials such as minerals and ores. Elemental carbon refers to the inorganic forms of carbon which can be found in crystalline and amorphous forms.
Crystalline forms have elemental carbon atoms arranged in a regular pattern while the carbon atoms in amorphous forms do not have regular patterns. The two crystalline forms of elemental carbon are diamonds and graphite. Diamond crystalline structure is formed by each carbon atom creating a covalent bond by sharing a pair of electrons with four other carbon atoms. Covalent bonds are the strongest chemical bonds known to mankind. Diamonds are the hardest known substances and the least volatile with a melting point of 6,242°F (3,550°C).
The crystalline structure of graphite is formed by carbon atoms creating tight hexagonal bonds with other atoms in the same plane, and a looser bond between atoms in different planes. A loose bond between planes makes graphite very soft and allows graphite to be used as a lubricant. Unlike diamonds, graphite is a good electrical conductor.
Before 1955, all diamonds came from natural deposits. In 1955, laboratory testing proved that applying high pressure and temperature to graphite in the presence of a catalyst could create synthetic diamonds. Synthetic diamonds mostly are used for industrial purposes.
Amorphous carbon is created when a material containing carbon is burned without sufficient oxygen to allow complete combustion. The resultant black carbon can be used to create dry-cell battery cores, inks, paints, and is a critical element in manufacturing rubber products. Black carbon also is the by-product of forest fires and insufficient combustion of fuels in automobiles, manufacturing plants, and coal-based electric generation. Diesel fuel creates more black carbon than gasoline during combustion. Black carbon can cause both health and environmental problems.
A fine particulate matter that can cause health problems is amorphous elemental carbon. Asthma and chronic bronchitis have been linked to black carbon, and there is some evidence that black carbon or soot may increase the risk for emphysema and lung cancer. Black carbon also is a factor in climate change. Since black carbon remains in the atmosphere for weeks rather than the century that carbon dioxide does, decreasing black carbon emissions is seen as one of the fastest ways to possibly reduce the effects of global climate change.