Isotopes of carbon

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Template:Short description Template:Redirect Template:More citations needed Template:Infobox carbon isotopes Carbon (6C) has 14 known isotopes, from Template:SimpleNuclide to Template:SimpleNuclide as well as Template:SimpleNuclide, of which only Template:SimpleNuclide and Template:SimpleNuclide are stable. The longest-lived radioisotope is Template:SimpleNuclide, with a half-life of 5700 years. This is also the only carbon radioisotope found in nature, as trace quantities are formed cosmogenically by the reaction Template:SimpleNuclide + Template:Subatomic particle → Template:SimpleNuclide + Template:SimpleNuclide. The most stable artificial radioisotope is Template:SimpleNuclide, which has a half-life of 20.34 minutes. All other radioisotopes have half-lives under 20 seconds, most less than 200 milliseconds. Lighter isotopes exhibit beta-plus decay into isotopes of boron and heavier ones beta-minus decay into isotopes of nitrogen, though at the limits particle emission occurs as well. The two lightest isotopes decay into helium via short-lived isotopes of lithium, beryllium and boron.

List of isotopes

Template:Anchor Template:Isotopes table |-id=Carbon-8 | Template:SimpleNuclide | style="text-align:right" | 6 | style="text-align:right" | 2 | Template:Val | style="text-align:center" | 1974 | Template:Val
[[[:Template:Val]]] | 2p | Template:SimpleNuclide[n 1] | 0+ | | |-id=Carbon-9 | rowspan=3|Template:SimpleNuclide | rowspan=3 style="text-align:right" | 6 | rowspan=3 style="text-align:right" | 3 | rowspan=3|Template:Val | rowspan=3 style="text-align:center" | 1964 | rowspan=3|Template:Val | β+ (Template:Val) | Template:SimpleNuclide[n 2] | rowspan=3|3/2− | rowspan=3| | rowspan=3| |- | β+α (Template:Val) | Template:SimpleNuclide[n 2] |- | β+p (Template:Val) | Template:SimpleNuclide[n 2] |-id=Carbon-10 | Template:SimpleNuclide | style="text-align:right" | 6 | style="text-align:right" | 4 | Template:Val | style="text-align:center" | 1949 | Template:Val | β+ | Template:SimpleNuclide | 0+ | | |- | rowspan=1|Template:SimpleNuclide[n 3] | rowspan=1 style="text-align:right" | 6 | rowspan=1 style="text-align:right" | 5 | rowspan=1 |Template:Val | style="text-align:center" | 1934 | rowspan=1 |Template:Val | β+ | Template:SimpleNuclide | rowspan=1 |3/2− | rowspan=1 | |-id=Carbon-12 | Template:SimpleNuclide | style="text-align:right" | 6 | style="text-align:right" | 6 | 12 exactly[n 4] | style="text-align:center" | 1919 | colspan=3 align=center|Stable | 0+ | colspan=2 style="text-align:center;"|[[[:Template:Val]], Template:Val][1] |-id=Carbon-13 | Template:SimpleNuclide[n 5] | style="text-align:right" | 6 | style="text-align:right" | 7 | Template:Val | style="text-align:center" | 1929 | colspan=3 align=center|Stable | 1/2− | colspan=2 style="text-align:center;"|[[[:Template:Val]], Template:Val][1] |-id=Carbon-14 | Template:SimpleNuclide[n 6] | style="text-align:right" | 6 | style="text-align:right" | 8 | Template:Val | style="text-align:center" | 1936 | Template:Val | β− | Template:SimpleNuclide | 0+ | colspan=2 style="text-align:center;"|Trace[n 7] |-id=Carbon-15 | Template:SimpleNuclide | style="text-align:right" | 6 | style="text-align:right" | 9 | Template:Val | style="text-align:center" | 1950 | Template:Val | β− | Template:SimpleNuclide | 1/2+ | | |-id=Carbon-16 | rowspan=2|Template:SimpleNuclide | rowspan=2 style="text-align:right" | 6 | rowspan=2 style="text-align:right" | 10 | rowspan=2|Template:Val | rowspan=2 style="text-align:center" | 1961 | rowspan=2|Template:Val | β−n (Template:Val) | Template:SimpleNuclide | rowspan=2|0+ | rowspan=2| | rowspan=2| |- | β− (Template:Val) | Template:SimpleNuclide |-id=Carbon-17 | rowspan=3|Template:SimpleNuclide | rowspan=3 style="text-align:right" | 6 | rowspan=3 style="text-align:right" | 11 | rowspan=3|Template:Val | rowspan=3 style="text-align:center" | 1968 | rowspan=3|Template:Val | β− (Template:Val) | Template:SimpleNuclide | rowspan=3|3/2+ | rowspan=3| | rowspan=3|

|- | β−n (Template:Val) | Template:SimpleNuclide |- | β−2n ? | Template:SimpleNuclide |-id=Carbon-18 | rowspan=3|Template:SimpleNuclide | rowspan=3 style="text-align:right" | 6 | rowspan=3 style="text-align:right" | 12 | rowspan=3|Template:Val | rowspan=3 style="text-align:center" | 1969 | rowspan=3|Template:Val | β− (Template:Val) | Template:SimpleNuclide | rowspan=3|0+ | rowspan=3| | rowspan=3| |- | β−n (Template:Val) | Template:SimpleNuclide |- | β−2n ? | Template:SimpleNuclide |-id=Carbon-19 | rowspan=3|Template:SimpleNuclide[n 8] | rowspan=3 style="text-align:right" | 6 | rowspan=3 style="text-align:right" | 13 | rowspan=3|Template:Val | rowspan=3 style="text-align:center" | 1974 | rowspan=3|Template:Val | β−n (Template:Val) | Template:SimpleNuclide | rowspan=3|1/2+ | rowspan=3| | rowspan=3| |- | β− (Template:Val) | Template:SimpleNuclide |- | β−2n (Template:Val) | Template:SimpleNuclide |-id=Carbon-20 | rowspan=3|Template:SimpleNuclide | rowspan=3 style="text-align:right" | 6 | rowspan=3 style="text-align:right" | 14 | rowspan=3|Template:Val | rowspan=3 style="text-align:center" | 1981 | rowspan=3|Template:Val | β−n (Template:Val) | Template:SimpleNuclide | rowspan=3|0+ | rowspan=3| | rowspan=3| |- | β−2n (< Template:Val) | Template:SimpleNuclide |- | β− (> Template:Val) | Template:SimpleNuclide |-id=Carbon-21 | Template:SimpleNuclide | style="text-align:right" | 6 | style="text-align:right" | 15 | Template:Val# | style="text-align:center" | (2015) | < Template:Val | n ? | Template:SimpleNuclide | 1/2+# | | |-id=Carbon-22 | rowspan=3|Template:SimpleNuclide[n 9] | rowspan=3 style="text-align:right" | 6 | rowspan=3 style="text-align:right" | 16 | rowspan=3|Template:Val | rowspan=3 style="text-align:center" | 1986 | rowspan=3|Template:Val | β−n (Template:Val) | Template:SimpleNuclide | rowspan=3|0+ | rowspan=3| | rowspan=3| |- | β−2n (< Template:Val) | Template:SimpleNuclide |- | β− (> Template:Val) | Template:SimpleNuclide Template:Isotopes table/footer

Carbon-11

Carbon-11 or Template:SimpleNuclide is a radioactive isotope of carbon that decays to boron-11 with a half-life to 20.34 minutes. This decay mainly occurs due to positron emission, with around 0.19–0.23% of decays instead occurring by electron capture.[2][3]

Template:SimpleNuclide → Template:SimpleNuclide + Template:SubatomicParticle + Template:SubatomicParticle + Template:Val
Template:SimpleNuclide + Template:SubatomicParticle → Template:SimpleNuclide + Template:SubatomicParticle + Template:Val

It is produced by hitting nitrogen with protons of around 16.5 MeV in a cyclotron. The causes the endothermic reaction[4][5]

Template:SimpleNuclide + Template:SubatomicParticle → Template:SimpleNuclide + Template:SimpleNuclide − 2.92 MeV

It can also be produced by fragmentation of Template:SimpleNuclide by shooting high-energy Template:SimpleNuclide at a target.[6]

Carbon-11 is commonly used as a radioisotope for the radioactive labeling of molecules in positron emission tomography. Among the many molecules used in this context are the radioligands [[DASB|[[[:Template:SimpleNuclide]]]DASB]] and [[25I-NBOMe|[[[:Template:SimpleNuclide]]]Cimbi-5]]. Due to the short half-life, the chemical reactions used to manipulate the radioisotope as generated and incorporate it into a biomolecule must be efficient. Popular key intermediates include [11C]phosgene,[7][8] for carboxylation-related reactions, though other synthons, such as [11C]carbonyl fluoride and [11C]carbon dioxide, are also being explored.[9] For methylation, [11C]iodomethane and related synthons are used.[9]

Stable isotopes

Template:Main Carbon-12 and carbon-13 account for approximately 98.9% and 1.1% (respectively) of the naturally occurring carbon on Earth.[10] However, the ratio of stable 13C and 12C in a material can vary due to differences in precursor source and isotopic fractionation induced by a variety of biogeochemical processes. The quantities of the different isotopes are commonly measured via isotope-ratio mass spectrometry and expressed as parts per thousand (‰ or "per mille") divergence from the ratio of a standard:[11]

δA13A2213C=((A13A2213CA12A2212C)sample(A13A2213CA12A2212C)standard−1)×1000 ‰

Peedee Belemnite ("PDB"), a fossil belemnite from the eponym Late Cretaceous geological formation in North and South Carolina (USA), was the original reference standard used for standardizing carbon isotope ratio values. Due to the depletion of the original PDB, an artificial "Vienna PDB" standard, or "VPDB", is generally used today.[12]

Paleoclimate

Template:SimpleNuclide and Template:SimpleNuclide are measured as the isotope ratio δ13C in benthic foraminifera and used as a proxy for nutrient cycling and the temperature dependent air–sea exchange of Template:CO2 (ocean ventilation).[13] Photosynthetic organisms, such as algae and plants find it easier to use the lighter carbon isotope (Template:SimpleNuclide) when they convert carbon dioxide and water into glucose and oxygen using sunlight and photosynthesis:

Template:Chem2

For example, large blooms of plankton (free-floating organisms) absorb large amounts of Template:SimpleNuclide from the oceans. Originally, the Template:SimpleNuclide was mostly incorporated into the seawater from the atmosphere. If the oceans that the plankton live in are stratified (meaning that there are layers of warm water near the top, and colder water deeper down), then the surface water does not mix very much with the deeper waters, so that when the plankton dies, it sinks and takes away Template:SimpleNuclide from the surface, leaving the surface layers relatively rich in Template:SimpleNuclide. Where cold waters well up from the depths (such as in the North Atlantic), the water carries Template:SimpleNuclide back up with it; when the ocean was less stratified than today, there was much more Template:SimpleNuclide in the skeletons of surface-dwelling species. Other indicators of past climate include the presence of tropical species and coral growth rings.[14]

Tracing food sources and diets

Different photosynthetic pathways preferentially select for the lighter Template:SimpleNuclide, but their selectivity differs.Template:Citation needed Grasses in temperate climates (barley, rice, wheat, rye, and oats, plus sunflower, potato, tomatoes, peanuts, cotton, sugar beet, and most trees and their nuts or fruits, roses, and Kentucky bluegrass) follow a C3 photosynthetic pathway that will yield δ13C values averaging about −26.5‰.Template:Citation needed Grasses in hot arid climates (maize in particular, but also millet, sorghum, sugar cane, and crabgrass) follow a C4 photosynthetic pathway that produces δ13C values averaging about −12.5‰.[15]

It follows that eating these different plants will affect the δ13C values in the consumer's body tissues. If an animal (or human) eats only C3 plants, their δ13C values will be from −18.5 to −22.0‰ in their bone collagen and −14.5‰ in the hydroxylapatite of their teeth and bones.[16]

In contrast, C4 feeders will have bone collagen with a value of −7.5‰ and hydroxylapatite value of −0.5‰.

In case studies, millet and maize eaters can easily be distinguished from rice and wheat eaters.Template:Citation needed Studying how these dietary preferences are distributed geographically through time can illuminate migration paths of people and dispersal paths of different agricultural crops. However, human groups have often mixed C3 and C4 plants (historically, northern Chinese subsisted on wheat (C3) and millet (C4)) or mixed plant and animal groups (for example, southeastern Chinese subsisting on rice and fish).[17]

Carbon-14

Template:Main

Carbon-14 (also called radiocarbon) occurs in trace amounts and has a half-life of 5730 years. The primary source of Template:SimpleNuclide on Earth is the reaction of Template:SimpleNuclide with thermal neutrons from cosmic radiation spallation reactions in the upper atmosphere; this mixes throughout the atmosphere, and biological processes such as photosynthesis incorporate the Template:SimpleNuclide into living organisms. Since organisms stop absorbing Template:SimpleNuclide upon dying, measurement of the amount of Template:SimpleNuclide in a sample may be used to estimate its age. This technique, called radiocarbon dating, is one of the principal methods of radiometric dating in archaeology.

See also

Daughter products other than carbon

References

Template:Reflist

Template:Navbox element isotopes Template:Authority control


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  14. ↑ Tim Flannery The weather makers: the history & future of climate change, The Text Publishing Company, Melbourne, Australia. Template:ISBN
  15. ↑ Template:Cite journal
  16. ↑ Template:Cite journal
  17. ↑ Template:Cite journal
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