Carbon 13 carbon dating
The crystal structure of graphite amounts to a parallel stacking of layers of carbon atoms.Within each layer the carbon atoms lie in fused hexagonal rings that extend infinitely in two dimensions.The notation used for the nucleus of atoms places the atomic mass as a presuperscript to the symbol of the element and the atomic number as a presubscript; thus, the isotope carbon-12 is symbolized C.Of the stable nuclides, the isotope carbon-13 is of particular interest in that its nuclear spin imparts response in a device called a nuclear magnetic resonance spectrometer, which is useful when investigating the molecular structures of covalently bonded compounds containing carbon.It is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds.It belongs to group 14 of periodic table 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 formed by the interaction of neutrons, produced by cosmic radiation, with nitrogen (N) in the atmosphere in a reaction that may be written as follows (neutron is symbolized as H): The carbon-14 atoms from this reaction are converted to carbon dioxide by reaction with atmospheric oxygen and mixed and uniformly distributed with the carbon dioxide containing stable carbon-12.Living organisms use atmospheric carbon dioxide, whether with stable or radioactive carbon, through processes of photosynthesis and respiration, and thus their systems contain the constant ratio of carbon-12 to carbon-14 that exists in the atmosphere.
The carbon-14 present in the dead substance decays in accordance with its 5,730-year (± 40 years) half-life, while the carbon-12 remains what it was at death.
The crystal structure of graphite is of a kind that permits the formation of many compounds, called lamellar or intercalation compounds, by penetration of molecules or ions.
Graphitic oxide and graphitic fluoride are nonconducting lamellar substances not obtained in true molecular forms that can be reproduced, but their formulas do approximate, respectively, the compositions of carbon dioxide and carbon monofluoride.carbon-13 (1.07 percent); 14 radioactive isotopes are known, of which the longest-lived is carbon-14, which has a half-life of 5,730 ± 40 years.
A less common form of graphite, which occurs in nature, is based upon an ABCABCA… The amorphous varieties of carbon are based upon microcrystalline forms of graphite.
The individual layers of carbon in graphite are called graphene, which was successfully isolated in single-layer form in 2004 by physicists Konstantin Novoselov and Andre Geim.
Thus, the extreme hardness, the high sublimation temperature, the presumed extremely high melting point (extrapolated from known behaviour), and the reduced chemical reactivity and insulating properties are all reasonable consequences of the crystal structure.