Array ( [0] => {{Short description|Isotope of Carbon}} [1] => {{For|the building in Oregon|Carbon12}} [2] => {{Infobox isotope [3] => | alternate_names = [4] => | symbol = C [5] => | image = Carbon-12.svg [6] => | mass_number = 12 [7] => | mass = 12 [8] => | num_neutrons = 6 [9] => | num_protons = 6 [10] => | abundance = 98.93% [11] => | parent = Nitrogen-12 [12] => | parent_symbol = N [13] => | parent_mass = 12 [14] => | parent_decay = [15] => | parent2 = Boron-12 [16] => | parent2_symbol = B [17] => | parent2_mass = 12 [18] => | parent2_decay = [19] => | spin = 0 [20] => | excess_energy = {{val|0.0}} [21] => | binding_energy = {{val|92161.753|0.014}} [22] => }} [23] => [24] => '''Carbon-12''' (12C) is the most abundant of the two [[Stable isotope|stable]] [[isotopes of carbon]] ([[carbon-13]] being the other), amounting to 98.93% of [[Periodic table|element]] [[carbon]] on Earth;{{cite web|url=http://www.ncsu.edu/ncsu/pams/chem/msf/pdf/IsotopicMass_NaturalAbundance.pdf |title=Table of Isotopic Masses and Natural Abundances |date=1999 }} its abundance is due to the [[triple-alpha process]] by which it is created in stars. Carbon-12 is of particular importance in its use as the standard from which [[atomic mass]]es of all [[nuclides]] are measured, thus, its atomic mass is exactly 12 [[Dalton (unit)|dalton]]s by definition. Carbon-12 is composed of 6 [[protons]], 6 [[neutrons]], and 6 [[electrons]]. [25] => [26] => == History == [27] => [28] => Before 1959, both the [[IUPAP]] and [[IUPAC]] used [[oxygen]] to define the [[Mole (unit)|mole]]; the chemists defining the mole as the number of atoms of oxygen which had mass 16 g, the physicists using a similar definition but with the [[oxygen-16]] isotope only. The two organizations agreed in 1959–60 to define the mole as follows. [29] => [30] =>
''Mole is the amount of substance of a system which contains as many elementary entities as there are atoms in 12 gram of carbon 12; its symbol is "mol".''
[31] => [32] => This was adopted by the [[CIPM|CIPM (International Committee for Weights and Measures)]] in 1967, and in 1971, it was adopted by the 14th [[CGPM|CGPM (General Conference on Weights and Measures)]]. [33] => [34] => In 1961, the isotope carbon-12 was selected to replace oxygen as the standard relative to which the atomic weights of all the other elements are measured.{{cite web|url=http://www.iupac.org/publications/ci/2004/2601/1_holden.html|title=Atomic Weights and the International Committee — A Historical Review|date=2004-01-26}} [35] => [36] => In 1980, the CIPM clarified the above definition, defining that the carbon-12 atoms are unbound and in their [[ground state]]. [37] => [38] => In 2018, IUPAC specified the mole as exactly {{val|6.02214076|e=23}} "elementary entities". The number of moles in 12 grams of carbon-12 became a matter of experimental determination. [39] => [40] => == Hoyle state == [41] => [[File:Hoyle state and possible decay way.svg|thumb|The Hoyle state and possible decay ways]] [42] => The '''Hoyle state''' is an excited, spinless, [[Resonance (particle physics)|resonant state]] of carbon-12. It is produced via the [[triple-alpha process]] and was predicted to exist by [[Fred Hoyle]] in 1954.{{cite journal |last=Hoyle |first=F. |year=1954 |title=On Nuclear Reactions Occurring in Very Hot Stars. I. the Synthesis of Elements from Carbon to Nickel |journal=The Astrophysical Journal Supplement Series |volume=1 |page=121 |issn=0067-0049 |doi=10.1086/190005 |bibcode=1954ApJS....1..121H }} The existence of the 7.7 MeV resonance Hoyle state is essential for the [[nucleosynthesis]] of carbon in helium-burning [[star]]s and predicts an amount of carbon production in a stellar environment which matches observations. The existence of the Hoyle state has been confirmed experimentally, but its precise properties are still being investigated.{{cite journal |last1=Freer |first1=M. |last2=Fynbo |first2=H. O. U. |title=The Hoyle state in 12C |journal=Progress in Particle and Nuclear Physics |date=2014 |volume=78 |pages=1–23 |doi=10.1016/j.ppnp.2014.06.001 |bibcode=2014PrPNP..78....1F |url=https://research.birmingham.ac.uk/portal/en/publications/the-hoyle-state-in-12c(f78d59b2-e838-4da3-a941-7946b44e5b32).html }} [43] => [44] => The Hoyle state is populated when a [[helium-4]] nucleus fuses with a [[beryllium-8]] nucleus in a high-temperature (108 [[kelvin|K]]) environment with densely concentrated (105 g/cm3) helium. This process must occur within 10−16 seconds as a consequence of the short half-life of 8Be. The Hoyle state also is a short-lived resonance with a half-life of {{val|2.4|e=-16|u=seconds}}; it primarily decays back into its three constituent [[alpha particle]]s, though 0.0413% of decays (or 1 in 2421.3) occur by [[internal conversion]] into the ground state of 12C.{{cite journal |last1=Alshahrani |first1=B. |last2=Kibédi |first2=T. |last3=Stuchberry |first3=A. E. |last4=Williams |first4=E. |last5=Fares |first5=S. |title=Measurement of the radiative branching ratio for the Hoyle state using cascade gamma decays |journal=EPJ Web of Conferences |date=2013 |volume=63 |pages=01022-1–01022-4 |doi=10.1051/epjconf/20136301022 |bibcode=2013EPJWC..6301022A |url=https://www.researchgate.net/publication/266560256 |doi-access=free |hdl=1885/101943 |hdl-access=free }} [45] => [46] => In 2011, an [[ab initio methods (nuclear physics)|ab initio]] calculation of the low-lying states of carbon-12 found (in addition to the [[ground state|ground]] and [[Excited state|excited]] spin-2 state) a resonance with all of the properties of the Hoyle state.{{cite journal |doi=10.1103/PhysRevLett.106.192501 |title=Ab Initio Calculation of the Hoyle State |year=2011 |last1=Epelbaum |first1=E. |last2=Krebs |first2=H. |last3=Lee |first3=D. |last4=Meißner |first4=U.-G. |journal=Physical Review Letters |volume=106 |pages=192501 |issue=19 |bibcode=2011PhRvL.106s2501E |pmid=21668146 |arxiv=1101.2547 |s2cid=33827991 }}{{cite magazine | doi = 10.1103/Physics.4.38 | url = http://physics.aps.org/viewpoint-for/10.1103/PhysRevLett.106.192501 | title = Viewpoint: The carbon challenge | year = 2011 | last1 = Hjorth-Jensen | first1 = M. | magazine = Physics | volume = 4 | pages = 38 | bibcode = 2011PhyOJ...4...38H | doi-access = free }} [47] => [48] => == Isotopic purification == [49] => [50] => The isotopes of carbon can be separated in the form of [[carbon dioxide]] gas by cascaded chemical exchange reactions with amine [[carbamate]].{{cite journal|author=Kenji Takeshita and Masaru Ishidaa|journal=Energy |volume=31|issue=15| date=December 2006|pages=3097–3107|title=Optimum design of multi-stage isotope separation process by exergy analysis|doi=10.1016/j.energy.2006.04.002}} [51] => [52] => == See also == [53] => [54] => * [[Avogadro constant]] [55] => * [[Carbon-11]] [56] => * [[Carbon-13]] [57] => * [[Carbon-14]] [58] => * [[Isotopes of carbon]] [59] => * [[Isotopically pure diamond]] [60] => * [[Mole (unit)]] [61] => [62] => == References == [63] => {{reflist}} [64] => [65] => == External links == [66] => *{{Cite web|last1=Jenkins|first1=David|last2=Kirsebom|first2=Oliver|date=2013-02-07|title=The secret of life|url=https://physicsworld.com/a/the-secret-of-life/|access-date=2021-08-27|website=Physics World|language=en-GB}} [67] => [68] => {{Isotope sequence [69] => |element=carbon [70] => |lighter=[[carbon-11]] [71] => |heavier=[[carbon-13]] [72] => |before=[[boron-12]], [[nitrogen-12]] [73] => |after=stable [74] => }} [75] => [76] => [[Category:Isotopes of carbon]] [] => )
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Carbon-12

Carbon-12 (12C) is the most abundant of the two stable isotopes of carbon (carbon-13 being the other), amounting to 98. 93% of element carbon on Earth; its abundance is due to the triple-alpha process by which it is created in stars.

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