Benoît Magimel
Antoine Roca
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Carbon (from Latin carbo 'coal') is a chemical element; it has symbol C and atomic number 6. It is nonmetallic and tetravalent —meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 electrons. It belongs to group 14 of the periodic table. [16]
Carbon is a multidisciplinary journal that publishes research on various forms and applications of carbon, such as nanotubes, graphene, fullerenes, and composites. The journal covers topics related to biology, catalysis, energy, environment, and smart materials, and features special issues and open access articles.
- Overview
- Properties and uses
- Production of elemental carbon
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carbon (C), nonmetallic chemical element in Group 14 (IVa) of the periodic table. Although widely distributed in nature, carbon is not particularly plentiful—it makes up only about 0.025 percent of Earth’s crust—yet it forms more compounds than all the other elements combined. In 1961 the isotope carbon-12 was selected to replace oxygen as the stan...
On a weight basis, carbon is 19th in order of elemental abundance in Earth’s crust, and there are estimated to be 3.5 times as many carbon atoms as silicon atoms in the universe. Only hydrogen, helium, oxygen, neon, and nitrogen are atomically more abundant in the cosmos than carbon. Carbon is the cosmic product of the “burning” of helium, in which three helium nuclei, atomic weight 4, fuse to produce a carbon nucleus, atomic weight 12.
In the crust of Earth, elemental carbon is a minor component. However, carbon compounds (i.e., carbonates of magnesium and calcium) form common minerals (e.g., magnesite, dolomite, marble, or limestone). Coral and the shells of oysters and clams are primarily calcium carbonate. Carbon is widely distributed as coal and in the organic compounds that constitute petroleum, natural gas, and all plant and animal tissue. A natural sequence of chemical reactions called the carbon cycle—involving conversion of atmospheric carbon dioxide to carbohydrates by photosynthesis in plants, the consumption of these carbohydrates by animals and oxidation of them through metabolism to produce carbon dioxide and other products, and the return of carbon dioxide to the atmosphere—is one of the most important of all biological processes.
Carbon as an element was discovered by the first person to handle charcoal from fire. Thus, together with sulfur, iron, tin, lead, copper, mercury, silver, and gold, carbon was one of the small group of elements well known in the ancient world. Modern carbon chemistry dates from the development of coals, petroleum, and natural gas as fuels and from the elucidation of synthetic organic chemistry, both substantially developed since the 1800s.
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Elemental carbon exists in several forms, each of which has its own physical characteristics. Two of its well-defined forms, diamond and graphite, are crystalline in structure, but they differ in physical properties because the arrangements of the atoms in their structures are dissimilar. A third form, called fullerene, consists of a variety of molecules composed entirely of carbon. Spheroidal, closed-cage fullerenes are called buckerminsterfullerenes, or “buckyballs,” and cylindrical fullerenes are called nanotubes. A fourth form, called Q-carbon, is crystalline and magnetic. Yet another form, called amorphous carbon, has no crystalline structure. Other forms—such as carbon black, charcoal, lampblack, coal, and coke—are sometimes called amorphous, but X-ray examination has revealed that these substances do possess a low degree of crystallinity. Diamond and graphite occur naturally on Earth, and they also can be produced synthetically; they are chemically inert but do combine with oxygen at high temperatures, just as amorphous carbon does. Fullerene was serendipitously discovered in 1985 as a synthetic product in the course of laboratory experiments to simulate the chemistry in the atmosphere of giant stars. It was later found to occur naturally in tiny amounts on Earth and in meteorites. Q-carbon is also synthetic, but scientists have speculated that it could form within the hot environments of some planetary cores.
Until 1955 all diamonds were obtained from natural deposits, most significant in southern Africa but occurring also in Brazil, Venezuela, Guyana, and Siberia. The single known source in the United States, in Arkansas, has no commercial importance; nor is India, once a source of fine diamonds, a significant present-day supplier. The primary source of diamonds is a soft bluish peridotic rock called kimberlite (after the famous deposit at Kimberley, South Africa), found in volcanic structures called pipes, but many diamonds occur in alluvial deposits presumably resulting from the weathering of primary sources. Isolated finds around the world in regions where no sources are indicated have not been uncommon.
Natural deposits are worked by crushing, by gravity and flotation separations, and by removal of diamonds by their adherence to a layer of grease on a suitable table. The following products result: (1) diamond proper—distorted cubic crystalline gem-quality stones varying from colourless to red, pink, blue, green, or yellow; (2) bort—minute dark crystals of abrasive but not gem quality; (3) ballas—randomly oriented crystals of abrasive quality; (4) macles—triangular pillow-shaped crystals that are industrially useful; and (5) carbonado—mixed diamond–graphite crystallites containing other impurities.
The successful laboratory conversion of graphite to diamond was made in 1955. The procedure involved the simultaneous use of extremely high pressure and temperature with iron as a solvent or catalyst. Subsequently, chromium, manganese, cobalt, nickel, and tantalum were substituted for iron. Synthetic diamonds are now manufactured in several countries and are being used increasingly in place of natural materials as industrial abrasives.
Graphite occurs naturally in many areas, the deposits of major importance being in China, India, Brazil, Turkey, Mexico, Canada, Russia, and Madagascar. Both surface- and deep-mining techniques are used, followed by flotation, but the major portion of commercial graphite is produced by heating petroleum coke in an electric furnace. A better crystallized form, known as pyrolytic graphite, is obtained from the decomposition of low-molecular-weight hydrocarbons by heat. Graphite fibres of considerable tensile strength are obtained by carbonizing natural and synthetic organic fibres.
Learn about carbon, a nonmetallic element that forms the basis of life and has many forms and applications. Explore its history, discovery, isotopes, and carbon cycle.
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Mar 12, 2022 · Carbon is an incredible element. Arrange carbon atoms in one way, and they become soft, pliable graphite. Rejigger the arrangement, and — presto! — the atoms form diamond, one of the hardest ...
Carbon is found in the sun and other stars, formed from the debris of a previous supernova. It is built up by nuclear fusion in bigger stars. It is present in the atmospheres of many planets, usually as carbon dioxide. On Earth, the concentration of carbon dioxide in the atmosphere is currently 390 ppm and rising.
Carbon fiber is used in making fishing rods, tennis rackets, airplanes as it is extraordinarily strong and light weight. Carbon has revolutionized nanotechnology by the discovery of carbon nanotubes, that are widely used in electronic industry. Carbon is widely used in carbonated and fuzzy drinks. It is used in various metallurgy processes.
Interesting Facts. - Carbon has the highest melting/sublimation point of all the elements and, in the form of diamond, also has the highest thermal conductivity of any element. - The isotope Carbon-14 is used in radiocarbon dating, which helps determine the age of ancient objects.
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