Carbon, a nonmetal, is the lightest element of Group IVA. Other members of the group are silicon (Si), germanium (Ge), tin (Sn), and lead (Pb).
The name is derived from the Latin word carbo for charcoal, and the symbol C is derived from the name.
Carbon, an element of prehistoric discovery, is very widely distributed. It is found in abundance in the sun, stars, and comets, and in the atmospheres of some planets.
Carbon is found free in nature as three different allotropes: graphite, diamond, and "fullerenes" or "bucky balls."
Graphite is one of the softest known materials while diamond is one of the hardest. Diamond - as gems - and graphite have been known for centuries. Indeed, during studies on air in 1770 Lavoisier demonstrated that diamonds could be combusted in the presence of air. The third allotropic form is fullerenes or "bucky balls." These are cages of carbon atoms (the best known of which is C60) and were discovered only in 1985.
In combination, carbon is found as carbon dioxide in the atmosphere of the earth and dissolved in all natural waters. It is a component of great rock masses in the form of carbonates of calcium (limestone), magnesium, and iron. (Calcite and aragonite are two mineral forms of CaCO3.) Coal, petroleum, and natural gas are chiefly hydrocarbons.
Carbon is unique among the elements in the vast number and variety of compounds it can form. With hydrogen, oxygen, and nitrogen, and other elements, it forms almost an infinite number of compounds, one carbon atom often being linked to many other carbon atoms. There are upwards of ten million known carbon compounds, many thousands of which are vital to organic and life processes. Without carbon, the basis for life would be impossible.
Carbon is added to molten iron in the production of steel, and carbon electrodes are widely used in electrical apparatus. The "lead" of the ordinary pencil is graphite mixed with clay. A common dry cell battery has a Zn metal anode, carbon cathode, and contains MnO2 and NH4Cl as well.
The successful linking in the 1940s of carbon with silicon has led to the development of a vast number of new substances known collectively as the silicones, polymers of silicon, oxygen, and organic groups. Some of them, as liquids, are used for lubrication at very low temperatures; others find use as plastics, in insulation, in rubber substitutes, and in waterproofing.
In 1961 the International Union of Pure and Applied Chemistry adopted the isotope carbon--12 as the basis for atomic weights. Carbon of atomic weight 14, a naturally occurring isotope that can also be produced in a nuclear reactor is radioactive and has a half life of 5,760 years. Carbon--14 is used as a "tracer" in chemical and biological processes and, using a technique developed and perfected by Libby in the 1940s, it has been widely used to date such materials as wood, archeological specimens, etc.