Carbon is a very important chemical element, with a chemical symbol of C. All known life on Earth needs it. Carbon has atomic mass 12 and atomic number 6. It is a nonmetal, meaning that it is not a metal.
|clear (diamond) & black (graphite)|
Diamond (left) and graphite (right), the two most well-known allotropes of carbon
Spectral lines of carbon
|Name, symbol, number||carbon, C, 6|
|Group, period, block||14, 2, p|
|Standard atomic weight||12.011(1) g/mol|
|Electron configuration||[He] 2s2 2p2|
|Electrons per shell||2, 4 (Image)|
|Density (near r.t.)||amorphous: 1.8–2.1 g/cm3|
|Density (near r.t.)||diamond: 3.515 g/cm3|
|Density (near r.t.)||graphite: 2.267 g/cm3|
|Sublimation point||3915 K, 3642 °C, 6588 °F|
|Triple point||4600 K (4327°C), 10800 kPa|
|Heat of fusion||117 (graphite) kJ/mol|
|Specific heat capacity||(25 °C) 6.155 (diamond)|
8.517 (graphite) J/(mol·K)
|Oxidation states||4, 3, 2, 1, 0, −1, −2, −3, −4|
|Electronegativity||2.55 (Pauling scale)|
||1st: 1086.5 kJ/mol|
|2nd: 2352.6 kJ/mol|
|3rd: 4620.5 kJ/mol|
|Covalent radius||77(sp³), 73(sp²), 69(sp) pm|
|Van der Waals radius||170 pm|
|Crystal structure note||(diamond, clear)|
|Thermal conductivity||(300 K) 900-2300 (diamond)|
119-165 (graphite) W/(m·K)
|Thermal expansion||(25 °C) 0.8 (diamond) µm/(m·K)|
|Speed of sound (thin rod)||(20 °C) 18350 (diamond) m/s|
|Young's modulus||1050 (diamond) GPa|
|Shear modulus||478 (diamond) GPa|
|Bulk modulus||442 (diamond) GPa|
|Poisson ratio||0.1 (diamond)|
|Mohs hardness||10 (diamond)|
|CAS registry number||7440-44-0|
|Most stable isotopes|
|Main article: Isotopes of carbon|
Chemistry of carbonEdit
A whole type of Chemistry, organic chemistry, is about carbon and its compounds. Carbon makes many types of compounds. Hydrocarbons are molecules with carbon and hydrogen. Methane, Propane, and many other fuels are hydrocarbons. Many of the substances that people use daily are organic compounds.
Carbon, hydrogen, nitrogen, oxygen, and some other elements like sulfur and phosphorus together form most life on earth (see Organic chemistry and List of biologically important elements). Carbon forms a very large number of organic compounds because it can form strong bonds with itself and with other elements. Because of the amounts of carbon living things have, all organic things are considered "carbon-based". Each carbon atom can form four single covalent bonds. These bonds allow carbon to form long chain-shaped molecules, called polymers, such as plastics.
Types of carbonEdit
Carbon in nature is found in three forms called allotropes: diamond, graphite, and fullerenes. Graphite, with clay, is in pencils. It is very soft. The carbon atoms in it make rings, which are on top of each other and slide very easily. Diamonds are the hardest natural mineral. Fullerenes are a "soccer ball" shape of carbon. They are mostly of interest to science. A special, man-made, tube-shaped allotrope of carbon is the carbon nanotube. Carbon nanotubes are very hard, so they might be used in armor. Nanotubes might be useful in nanotechnology. There are 10 million known carbon compounds.
A radioactive isotope of carbon, carbon-14, can be used to figure out how old some objects are or when something died. As long as something is on the surface of the earth and taking in carbon, the amount of carbon-14 stays the same. When an object stops taking in carbon, the carbon-14 amount goes down. Because the half-life (how long it takes for half of a radioactive isotope to go away) of carbon-14 is 5730 years, scientists can see how old the object is by how much carbon-14 is left.
Where carbon isEdit
Carbon is important to the human body and other living things, and it is the second most common element in the human body, at 23% of all body weight. It is also a key part of many biological molecules (molecules used in life).
Most of the carbon on Earth is coal. Graphite is in many (typically desert) areas, including Sri Lanka, Madagascar, and Russia. Diamonds are rare and are found largely in Africa. Carbon is also in some meteorites.
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- Haaland, D (1976). "Graphite-liquid-vapor triple point pressure and the density of liquid carbon". Carbon 14 (6): 357. doi:10.1016/0008-6223(76)90010-5.
- Savvatimskiy, A (2005). "Measurements of the melting point of graphite and the properties of liquid carbon (a review for 1963–2003)". Carbon 43 (6): 1115. doi:10.1016/j.carbon.2004.12.027.
- "Fourier Transform Spectroscopy of the System of CP" (PDF). Retrieved 2007-12-06.
- "Fourier Transform Spectroscopy of the Electronic Transition of the Jet-Cooled CCI Free Radical" (PDF). Retrieved 2007-12-06.
- "Carbon: Binary compounds". Retrieved 2007-12-06.
- Magnetic susceptibility of the elements and inorganic compounds, in Handbook of Chemistry and Physics 81st edition, CRC press.
- Properties of diamond, Ioffe Institute Database
- Emsley, John (2001). Nature's Building blocks. Oxford University Press. ISBN 0-19-850341-5. Check
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- University of Sheffield and Webelements Ltd. (2007). "Chemistry : Periodic Table : carbon : key information".