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This exothermic reaction is used in the iron and steel industry to smelt iron and to control the carbon content of steel: Carbon combines with some metals at high temperatures to form metallic carbides, such as the iron carbide cementite in steel and tungsten carbide, widely used as an abrasive and for making hard tips for cutting tools.The system of carbon allotropes spans a range of extremes: Atomic carbon is a very short-lived species and, therefore, carbon is stabilized in various multi-atomic structures with different molecular configurations called allotropes.The three relatively well-known allotropes of carbon are amorphous carbon, graphite, and diamond.Once considered exotic, fullerenes are nowadays commonly synthesized and used in research; they include buckyballs, The amorphous form is an assortment of carbon atoms in a non-crystalline, irregular, glassy state, not held in a crystalline macrostructure.The largest sources of inorganic carbon are limestones, dolomites and carbon dioxide, but significant quantities occur in organic deposits of coal, peat, oil, and methane clathrates.Carbon forms a vast number of compounds, more than any other element, with almost ten million compounds described to date, The allotropes of carbon include graphite, one of the softest known substances, and diamond, the hardest naturally occurring substance.In general, covalent radius decreases with lower coordination number and higher bond order.Carbon compounds form the basis of all known life on Earth, and the carbon–nitrogen cycle provides some of the energy produced by the Sun and other stars.
It is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds. Carbon is the 15th most abundant element in the Earth's crust, and the fourth most abundant element in the universe by mass after hydrogen, helium, and oxygen.
C) For the best possible precision, carbon isotopic compositions of gas components are done by conventional off-line methods consisting of chromatographic separation followed by combustion and dual-inlet isotope ratio mass spectrometry.
Reproducibility is generally 0.1 per mil or better.
Graphite is soft enough to form a streak on paper (hence its name, from the Greek verb "γράφειν" which means "to write"), while diamond is the hardest naturally occurring material known.
Graphite is a good electrical conductor while diamond has a low electrical conductivity.