Carbon
Carbon is the sixth element, with a ground-state electron configuration of 1s22s22p2. Its four outer electrons are valence electrons that allow it to form up to four covalent bonds. This tetravalent nature defines its chemical behavior across all known compounds. The first four ionization energies for carbon are 1086.5, 2352.6, 4620.5 and 6222.7 kJ/mol. These values are much higher than those of heavier group-14 elements like silicon or germanium. Carbon's electronegativity measures 2.5 on the Pauling scale. This value sits close to most nearby nonmetals and some transition metals. Covalent radii vary depending on bond order. A single C-C bond measures 77.2 pm while a triple bond shrinks to 60.3 pm. These atomic properties enable carbon to build stable chains and rings under Earth conditions.
Graphite consists of layers of hexagonally arranged carbon atoms stacked loosely together. Weak van der Waals forces hold these sheets in place allowing them to slip past one another easily. This structure makes graphite soft enough to leave a streak on paper. Diamond features a rigid three-dimensional lattice where each atom bonds tetrahedrally to four others. This arrangement creates the hardest naturally occurring substance known to science. Under normal pressure diamond is thermodynamically unstable but transforms into graphite so slowly that it remains unchanged for billions of years. Fullerenes emerged as synthetic crystalline forms with warped structures containing pentagons and heptagons alongside hexagons. Buckyballs form spherical shapes while nanotubes create hollow cylinders. Graphene stands as a two-dimensional sheet of carbon atoms arranged in a hexagonal lattice. As of 2009 researchers found graphene to be the strongest material ever tested. Carbon nanofoam discovered in 1997 exhibits ferromagnetism and has a density of about 2 kg/m³. Q-carbon developed in 2015 shows hardness superior to diamonds along with fluorescence.
Carbon ranks fourth most abundant chemical element in the observable universe by mass after hydrogen helium and oxygen. Formation occurs within giant or supergiant stars through the triple-alpha process requiring temperatures over 100 megakelvins. Three alpha particles collide nearly simultaneously to forge carbon nuclei from helium fusion products. Lithium-5 and beryllium-8 decay almost instantly back into smaller nuclei preventing significant creation during the Big Bang. When massive stars die as supernovae they scatter carbon into space as dust. This dust becomes component material for next-generation star systems with accreted planets. The Solar System contains an abundance of carbon enabling life as we know it. Rotational transitions of isotopic forms like CO13 are detectable in submillimeter wavelengths. These signals help astronomers study newly forming stars in molecular clouds. More than 20% of cosmic carbon may associate with polycyclic aromatic hydrocarbons formed billions of years after the Big Bang. Carbon-rich asteroids remain preponderant in outer parts of the asteroid belt though no direct sampling has occurred yet.
Photosynthetic plants draw carbon dioxide from atmosphere or seawater building biomass through the Calvin cycle. Some carbon enters oceans where bacteria consume dissolved compounds while dead matter becomes petroleum or coal. Animals exhale carbon dioxide consuming plant or animal biomass in return. About 900 gigatonnes of carbon exist in Earth's atmosphere today. Dissolved carbon reaches approximately 36,000 gigatonnes within all water bodies. Biosphere estimates place carbon at 550 gigatonnes despite large uncertainty regarding deep subsurface bacteria levels. Coal reserves amount to around 900 gigatonnes representing 80% of fossil fuel sources. Oil reserves reach about 150 gigatonnes while natural gas holds roughly 105 gigatonnes of carbon. From 1751 to 2008 humans released 347 gigatonnes of carbon dioxide into the atmosphere burning fossil fuels. Methane hydrates store between 500 and 3,000 gigatonnes beneath polar regions and ocean floors. Carbon-14 forms in upper troposphere layers by cosmic ray interaction with nitrogen-14 nuclei. This radioisotope decays with a half-life of 5,700 years enabling radiocarbon dating invented in 1949.
Carbon forms very long chains of interconnecting carbon-carbon bonds called catenation. These strong stable bonds allow creation of countless compounds including hydrocarbons. Hydrocarbon backbones can substitute hydrogen atoms with heteroatoms like oxygen nitrogen sulfur phosphorus or halogens. Functional groups recur across organic molecules conferring common reactivity patterns for systematic study. When united with hydrogen carbon creates various hydrocarbons used as refrigerants lubricants solvents and chemical feedstock. Combined with oxygen and hydrogen it forms sugars lignans chitins alcohols fats aromatic esters carotenoids and terpenes. Nitrogen addition produces alkaloids while sulfur yields antibiotics amino acids and rubber products. Phosphorus incorporation enables DNA RNA adenosine triphosphate ATP and other energy-transfer molecules. Norman Horowitz head of Mariner and Viking missions considered unique carbon characteristics unlikely to be replaced even on another planet. Over two hundred million carbon-containing compounds have been described and indexed yet remain only a fraction theoretically possible under standard conditions. Carbon occurs in all known organic life serving as basis for organic chemistry itself.
The English name carbon derives from Latin carbo meaning coal and charcoal. French charbon shares this root while German Kohlenstoff literally translates to coal-substance. Diamonds were known probably as early as 2500 BCE in China. Charcoal production mimics modern chemistry by heating wood inside clay-covered pyramids excluding air. René Antoine Ferchault de Réaumur demonstrated iron transformation into steel through substance absorption in 1722. Antoine Lavoisier showed diamonds are carbon form when burning samples releasing equal amounts of carbon dioxide per gram in 1772. Carl Wilhelm Scheele proved graphite identical with charcoal plus small iron admixture in 179 giving aerial acid upon oxidation. Claude Louis Berthollet Gaspard Monge and C. A. Vandermonde confirmed graphite composition mostly carbon by oxidizing it in oxygen in 1786. Lavoisier listed carbon as element in his 1789 textbook proposing carbone as name. Fullerene discovered in 1985 includes nanostructured forms like buckyballs and nanotubes. Robert Curl Harold Kroto and Richard Smalley received Nobel Prize in Chemistry for fullerenes in 1996.
Commercially viable natural graphite deposits occur globally but most important sources lie in China India Brazil and North Korea. World production reached 1.1 million tonnes in 2010 with China contributing 800,000 tonnes. Synthetic graphite valued at $998 million was produced in United States during 2009. Diamond supply chain controlled by limited powerful businesses concentrated in few locations worldwide. Only tiny fraction of diamond ore consists actual diamonds requiring careful crushing to prevent destruction. Before X-ray fluorescence common practice used grease belts exploiting stronger sticking tendency of diamonds. Primary deposit production started in South Africa during 1870s after discovery of diamond fields. Accumulated total exceeds 4.5 billion carats mined since then. Russia produced almost one-fifth global output by 2005 while Argyle mine became largest source producing 14 million carats in 2018. About 80% mined diamonds equal 100 million carats annually relegated industrial use known as bort. Synthetic diamonds invented 1950s produce 3 billion carats yearly using high pressure methods or chemical vapor deposition. Carbon fiber made pyrolyzing polyacrylonitrile filaments creates lightweight composite materials reinforcing plastics. Industrial applications include cutting drilling grinding polishing tools for machining metals and stone.
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Common questions
What is the electron configuration of carbon?
Carbon has a ground-state electron configuration of 1s22s22p2. Its four outer electrons are valence electrons that allow it to form up to four covalent bonds.
When was radiocarbon dating invented and what is its half-life?
Radiocarbon dating was invented in 1949 using Carbon-14 which decays with a half-life of 5,700 years. This radioisotope forms in upper troposphere layers by cosmic ray interaction with nitrogen-14 nuclei.
Which countries produce the most natural graphite deposits globally?
Most important sources of commercially viable natural graphite lie in China India Brazil and North Korea. World production reached 1.1 million tonnes in 2010 with China contributing 800,000 tonnes.
Who discovered fullerenes and when did they receive their Nobel Prize?
Robert Curl Harold Kroto and Richard Smalley discovered fullerenes in 1985. They received the Nobel Prize in Chemistry for this discovery in 1996.
How much carbon exists in Earth's atmosphere today compared to water bodies?
About 900 gigatonnes of carbon exist in Earth's atmosphere today while dissolved carbon reaches approximately 36,000 gigatonnes within all water bodies.