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Carbon-12
 
 
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Carbon-12 is the most abundant
Abundance (chemistry)

In a chemical reaction, a reactant is considered to be in abundance if the quantity of that substance is high and virtually unchanged by the reaction....
 of the two stable
Stable isotope

Stable isotopes are chemical Isotope that are not radioactive . By this definition, there are 256 known stable isotopes of the 80 elements which have one or more stable isotopes....
 isotope
Isotope

Isotopes are any of the different types of atoms of the same chemical element, each having a different atomic mass . Isotopes of an element have atomic nucleus with the same number of protons but different numbers of neutron....
s of the element carbon
Carbon

Carbon is a chemical element with chemical symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalence?making four electrons available to form covalent bond chemical bonds....
, accounting for 98.89% of carbon; it contains 6 protons, 6 neutrons, and 6 electrons.

Carbon-12 is of particular importance as it is used as the standard from which atomic mass
Atomic mass

The atomic mass is the mass of an atom, most often expressed in Atomic mass units. The atomic mass may be considered to be the total mass of protons, neutrons and electrons in a single atom ....
es of all nuclides are measured: its mass number is by definition 12.

History
Prior to 1959 both the IUPAP and IUPAC tended to use oxygen
Oxygen

Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]...
 to define the mole
Mole (unit)

The mole is a Units of measurement of amount of substance: it is an SI base unit, and one of the few units used to measure this physical quantity....
, 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.






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Carbon-12 is the most abundant
Abundance (chemistry)

In a chemical reaction, a reactant is considered to be in abundance if the quantity of that substance is high and virtually unchanged by the reaction....
 of the two stable
Stable isotope

Stable isotopes are chemical Isotope that are not radioactive . By this definition, there are 256 known stable isotopes of the 80 elements which have one or more stable isotopes....
 isotope
Isotope

Isotopes are any of the different types of atoms of the same chemical element, each having a different atomic mass . Isotopes of an element have atomic nucleus with the same number of protons but different numbers of neutron....
s of the element carbon
Carbon

Carbon is a chemical element with chemical symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalence?making four electrons available to form covalent bond chemical bonds....
, accounting for 98.89% of carbon; it contains 6 protons, 6 neutrons, and 6 electrons.

Carbon-12 is of particular importance as it is used as the standard from which atomic mass
Atomic mass

The atomic mass is the mass of an atom, most often expressed in Atomic mass units. The atomic mass may be considered to be the total mass of protons, neutrons and electrons in a single atom ....
es of all nuclides are measured: its mass number is by definition 12.

History


Prior to 1959 both the IUPAP and IUPAC tended to use oxygen
Oxygen

Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]...
 to define the mole
Mole (unit)

The mole is a Units of measurement of amount of substance: it is an SI base unit, and one of the few units used to measure this physical quantity....
, 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 1959/1960 to define the mole as:

"The mole is the amount of substance of a system which contains as many elementary

entities as there are atoms in 0.012 kilogram
Kilogram

The kilogram or kilogrammeThe spelling kilogram is used by the International Committee for Weights and Measures and the U.S....
 of carbon 12; its symbol is "mol.""


This was adopted by the CIPM (International Committee for Weights and Measures) in 1967, and in 1971 it was adopted by the 14th CGPM (General Conference on Weights and Measures).

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

In 1980 the CIPM clarified the above definition, defining that the carbon-12 atoms are unbound and in their ground state.

Hoyle State

The Hoyle State is an excited state of carbon-12 with precisely the properties necessary to allow just the right amount of carbon to be created in a stellar environment. The existence of the Hoyle state is essential for the nucleosynthesis of carbon
Carbon

Carbon is a chemical element with chemical symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalence?making four electrons available to form covalent bond chemical bonds....
 in helium-burning red giant stars. The resonant state was predicted by Fred Hoyle in the 1950s based on the observed abundances of heavy elements in the universe. The resonant state allows carbon to be produced via the triple-alpha process
Triple-alpha process

The triple alpha process is a set of nuclear fusion reactions by which three helium nuclei are transformed into carbon.Older stars start to accumulate helium produced by the proton-proton chain reaction and the CNO cycle in their cores....
. The existence of the Hoyle state has been confirmed but its precise properties are still being investigated.

See also


  • Carbon
    Carbon

    Carbon is a chemical element with chemical symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalence?making four electrons available to form covalent bond chemical bonds....
  • Carbon-13
    Carbon-13

    Carbon-13 is a natural, Stable isotope isotope of carbon and one of the environmental isotopes. It makes up about 1.1% of all natural carbon on Earth....
  • Carbon-14
    Carbon-14

    Carbon-14, 14C, or radiocarbon, is a radioactive isotope of carbon discovered on February 27, 1940, by Martin Kamen and Sam Ruben at the University of California Radiation Laboratory in Berkeley, California, though its existence had been suggested already in 1934 by Franz Kurie....
  • Isotopes of carbon
    Isotopes of carbon

    Carbon Standard atomic mass: 12.0107 unified atomic mass unit...
  • Mole (unit)
    Mole (unit)

    The mole is a Units of measurement of amount of substance: it is an SI base unit, and one of the few units used to measure this physical quantity....
  • Avogadro constant


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