It is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds. There are three naturally occurring isotopes, with 12C and 13C being stable, while 14C is radioactive, decaying with a half-life of about 5,730 years. Carbon is one of the few elements known since antiquity.
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. It is present in all forms of carbon-based life, and in the human body carbon is the second most abundant element by mass (about 18.5%) after oxygen. This abundance, together with the unique diversity of organic compounds and their unusual polymer-forming ability at the temperatures commonly encountered on Earth, make this element the chemical basis of all known life.
The atoms of carbon can be bonded together in different ways: allotropes of carbon. The best known are graphite, diamond, and amorphous carbon. The physical properties of carbon vary widely with the allotropic form. For example, graphite is opaque and black, while diamond is highly transparent. Graphite is soft enough to form a streak on paper (hence its name, from the Greek word "γράφω" which means "to write"), while diamond is the hardest naturally-occurring material known. Graphite is a very good conductor, while diamond has a very low electrical conductivity. Under normal conditions, diamond, carbon nanotubes, and graphene have the highest thermal conductivities of all known materials. All carbon allotropes are solids under normal conditions, with graphite being the most thermodynamically stable form. They are chemically resistant and require high temperature to react even with oxygen.
The most common oxidation state of carbon in inorganic compounds is +4, while +2 is found in carbon monoxide and other transition metal carbonyl complexes. 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, which in turn are a tiny fraction of such compounds that are theoretically possible under standard conditions.
Carbon. Carbon (from Latin: carbo "coal") is a chemical element with symbol C and atomic number 6.
On the Periodic table, it is the first (row 2) of six elements in column (group) 14, which have in common the composition of their outer electron shell. It is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds.
Compounds of Carbon. History and Etymology. Production. Applications. Precautions. Acheson process. Cross-section of an Acheson furnace The Acheson process is a process to synthesize graphite and silicon carbide, named after its inventor Edward Goodrich Acheson.
In the furnace, an electric current was passed through a graphite core, surrounded by sand, salt, and carbon. The electric current heated the graphite and other materials, allowing them to react, producing a layer of silicon carbide around the graphite core. The process gives off carbon monoxide. There are four chemical reactions in the process that produces silicon carbide (SiC): C + SiO2 → SiO + COSiO2 + CO → SiO + CO2C + CO2 → 2CO2C + SiO → SiC + CO The first light emitting diodes were produced using silicon carbide from the Acheson process.
The first commercial plant using the Acheson process was built by Acheson in Niagara Falls, New York, where hydroelectric plants nearby could cheaply produce the necessary power for the energy intensive process. References Further reading Fullerene. The discovery of fullerenes greatly expanded the number of known carbon allotropes, which until recently were limited to graphite, graphene, diamond, and amorphous carbon such as soot and charcoal.
Buckyballs and buckytubes have been the subject of intense research, both for their unique chemistry and for their technological applications, especially in materials science, electronics, and nanotechnology. History The icosahedral fullerene C540, another member of the family of fullerenes. The icosahedral C60H60 cage was mentioned in 1965 as a possible topological structure. Eiji Osawa of Toyohashi University of Technology predicted the existence of C60 in 1970. He noticed that the structure of a corannulene molecule was a subset of a Association football shape, and he hypothesised that a full ball shape could also exist.
Japanese scientific journals reported his idea, but it did not reach Europe or the Americas. Exfoliated graphite nano-platelets. Exfoliated graphite nano-platelets (xGnP) are new types of nanoparticles made from graphite.
These nanoparticles consist of small stacks of graphene that are 1 to 15 nanometers thick, with diameters ranging from sub-micrometre to 100 micrometres. The X-ray diffractogram of this material would resemble that of graphite, in that the 002 peak would still appear at ~26o 2 theta. However, the peak would appear considerably smaller and broader. These features indicate that the interplanar distance in exfoliated graphite is similar to that of the parent graphite, but the stack size (of graphene layers) is small. Since xGnP is composed of the same material as carbon nanotubes, it shares many of their electrochemical characteristics, although not their tensile strength.
Carbon fibers. This article is about loose or woven carbon filament.
For the rigid composite material made from carbon fiber used in aerospace and other applications, see Carbon fiber reinforced polymer. Fabric made of woven carbon filaments Carbon fiber or carbon fibre (alternatively CF, graphite fiber or graphite fibre) is a material consisting of fibers about 5–10 micrometres in diameter and composed mostly of carbon atoms. Intumescent. An intumescent is a substance that swells as a result of heat exposure, thus increasing in volume and decreasing in density.
Intumescents are typically used in passive fire protection and, in the U.S., require listing and approval use and compliance in their installed configurations in order to comply with the law.  Lonsdaleite. Lonsdaleite (named in honour of Kathleen Lonsdale), also called hexagonal diamond in reference to the crystal structure, is an allotrope of carbon with a hexagonal lattice.
In nature, it forms when meteorites containing graphite strike the Earth. The great heat and stress of the impact transforms the graphite into diamond, but retains graphite's hexagonal crystal lattice. Lonsdaleite was first identified in 1967 from the Canyon Diablo meteorite, where it occurs as microscopic crystals associated with diamond. It is translucent, brownish-yellow, and has an index of refraction of 2.40 to 2.41 and a specific gravity of 3.2 to 3.3. Its hardness is theoretically superior to that of cubic diamond (up to 58% more) according to computational simulations but natural specimens exhibited somewhat lower hardness through a large range of values (from 7 to 8 on Mohs hardness scale). Passive fire protection. Passive Fire Protection (PFP) is an integral component of the three components of structural fire protection and fire safety in a building.
PFP attempts to contain fires or slow the spread, through use of fire-resistant walls, floors, and doors (amongst other examples). PFP systems must comply with the associated Listing and approval use and compliance in order to provide the effectiveness expected by building codes. Structural fire protection Fire protection in a building, offshore facility or a ship is a system that includes: Pyrolytic carbon. Sheets of pyrolytic carbon Pyrolytic carbon is a material similar to graphite, but with some covalent bonding between its graphene sheets as a result of imperfections in its production.
Pyrolytic carbon is man-made and not found in nature. Generally it is produced by heating a hydrocarbon nearly to its decomposition temperature, and permitting the graphite to crystallise (pyrolysis). One method is to heat synthetic fibers in a vacuum. CNO cycle. Triple-alpha process. "Helium burning" redirects here.
It is not to be confused with alpha process. Overview of the triple-alpha process. The triple-alpha process is a set of nuclear fusion reactions by which three helium-4 nuclei (alpha particles) are transformed into carbon. Older stars start to accumulate helium produced by the proton–proton chain reaction and the carbon–nitrogen–oxygen cycle in their cores. The products of further nuclear fusion reactions of helium with hydrogen or another helium nucleus produce lithium-5 and beryllium-8 respectively, both of which are highly unstable and decay almost instantly back into smaller nuclei. When the star starts to run out of hydrogen to fuse, the core of the star begins to collapse until the central temperature rises to 108 K (8.6 keV).
Once beryllium-8 is produced a little faster than it decays, the number of beryllium-8 nuclei in the stellar core increases to a large number. Carbon chauvinism. Carbon chauvinism is a neologism meant to disparage the assumption that the chemical processes of hypothetical extraterrestrial life must be constructed primarily from carbon (organic compounds) because carbon's chemical and thermodynamic properties render it far superior to all other elements. Concept The term was used as early as 1973, when scientist Carl Sagan described it and other human chauvinisms that limit imagination of possible extraterrestrial life. It suggests that human beings, as carbon-based life forms who have never encountered any life that has evolved outside the Earth’s environment, may find it difficult to envision radically different biochemistries.