what type of reaction occurs when carbon-14 changes to carbon-12?

Employ of Carbon-14 in Radiocarbon Dating Chemistry Tutorial

Key Concepts

Naturally occurring carbon is fabricated up of 3 isotopes :
⚛ carbon-12

⚛ carbon-xiii

⚛ carbon-fourteen
Of these isotopes, the most mutual in nature is carbon-12
Ii of these isotopes are stable :
⚛ carbon-12

⚛ carbon-thirteen
One of the isotopes, carbon-14, is unstable.
Carbon-14 is formed naturally in the atmosphere.
Living things comprise carbon (carbon-12, carbon-13 and carbon-14) into their cells until they dice.
At death, no new carbon is added to the cells, but the radioactive carbon-14 continues to undergo nuclear disuse (radioactive decay) and so overtime the corporeality of carbon-14 in the cells decreases.
Radiocarbon dating compares the present ratio of carbon-xiv to carbon-12 to determine how long ago the living thing died.

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How Carbon-fourteen is Incorporated Into Living Things

Carbon-14 (^xivC) is produced in the temper by the interaction of neutrons (ⁱn) produced by cosmic rays with the stable isotope of nitrogen, nitrogen-14 (^xivN):

The carbon-xiv atoms produced are so incorporated into carbon dioxide (CO₂) molecules to produce ^xivCO_two molecules which mix with the well-nigh common ¹²CO₂ molecules in the atmosphere.

The ¹⁴CO₂ enters establish tissue as a result of photosynthesis or absorption through the roots.

¹⁴C enters brute tissue when animals eat plants containing ¹⁴C.

The amount of ¹⁴C produced in the atmosphere is balanced past the continual nuclear decay (radioactive decay) of ¹⁴C to produce ¹⁴N and a beta-particle:

Radiocarbon Dating

When a found or animal dies it stops taking in carbon-14 and radioactive decay begins to subtract the amount of carbon-14 in the tissues.

The historic period of the plant or animate being specimen containing carbon, such equally wood, bones, plant remains, is adamant by measuring the ratio of carbon-12 to carbon-14.

The half-life of carbon-14 is only 5730 years.
Because of this relatively short half-life, carbon-14 can only be used to date specimens upward to almost 45,000 years old.
Afterwards this the corporeality of carbon-14 present in the sample is too small to be measured precisely.
Carbon-fourteen can not be used to measure the age of very young specimens as the difference between the amount of carbon-12 and carbon-fourteen volition non exist sufficient to be detected.

Carbon-14 dating relies on the post-obit assumptions:

the initial action of carbon-xiv in plant and animal tissues is a abiding (carbon-fourteen activity is independent of fourth dimension and geographical location)
the specimen has not been contaminated with modern carbon-14

It is known that the radiocarbon content of the temper has varied in the by, and then the initial activity of carbon-14 has Non been a abiding.
The post-obit variations in carbon-14 activity take been noted:

In 1958 de Vries showed that the carbon-fourteen action effectually 1700 and 1500 A.D. was up to 2% greater than in the 1900'south (this is known as the de Vries Effect)
In 1955 Suess constitute that the activity of twentieth century woods is well-nigh ii% lower than that of nineteenth century wood (this is known equally the Suess Effect)

There are a number of possible reasons for the variation in radiocarbon content of the atmosphere:
Possible explanations include:

changes in the cosmic ray flux due to the activity of the sun
changes in the Earth's magnetic field which modulates the proton flux which in plough affects the rate of production of carbon-14
increased CO₂ in the temper due to the combustion of fossil fuels since the get-go of the Industrial Revolution
the explosion of nuclear devices and the operation of nuclear reactors since 1945 has profoundly increased the level of carbon-14 activity

Calibration curves take been produced by comparing radiocarbon dates with other dating methods such equally dendrochronology (a dating method using the tree'due south growth rings).
This allows corrections to be made on radiocarbon dates in order to produce more accurate dates.

Materials that tin can be Dated using the Carbon-xiv Method

Radiocarbon dating, or carbon-14 dating, can be used to date material that had its origins in a living matter as long as the material contains carbon.
Some materials that practise not contain carbon, like clay pots, can be dated if they were fired in an oven (burnt) and contain carbon as a effect of this.
It should exist noted that information technology is non the artefact that is beingness dated, it is the soot, ash or charring.

The table below lists some materials that are dated using radiocarbon dating and comments on the reliability of the results:

Material	Amount required in grams	Comments
charcoal and forest	25	Usually reliable
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grains, seeds, nutshells, grasses, twigs, cloth, paper, hide, burnt bones	25	Normally reliable

organic material mixed with soil	50-300	Every bit much soil equally possible must exist removed from the specimen for the appointment to be reliable

peat	fifty-200	Reliable if roots of modern plants are removed

ivory	50	Usually reliable, just the interior of tusks is younger than the exterior

charred bones	300	Heavily charred bones requite reliable dates but lightly charred bones give unreliable dates considering of carbon exchange with modern carbon-xiv

inorganic carbon in shells	100	not very reliable due to carbon exchange with carbon-14 in waters containing carbonate

pottery and iron	2000 - 5000	Often reliable. Carbon-14 is incorporated into the pottery or iron at the fourth dimension it was made

A Brief History of Carbon-14 Dating Methods

1934, A.5. Grosse published a paper reporting that the mineral eudialyte independent radioactivity in backlog of that expected.
He suggested that this was due to the presence of isotopes produced by the interaction of catholic rays with elements such as oxygen, silicon, iron, and zirconium.
(cosmic ray neutrons were discovered by Locker in 1933)
1934, F.N.D. Kurie exposed nitrogen to fast neutrons and observed some nitrogen nuclei emit a particle that made a long, thin runway in a cloud chamber
1936, Burcham and Goldhaber showed this to be a reaction of nitrogen-xiv with a neutron producing carbon-14 and a proton.
1939, C.G. and D.D. Montgomery suggested carbon-fourteen could be produced in the atmosphere by the interaction of catholic ray neutrons with nitrogen-14
1940, Kamen prepared a measurable quantity of carbon-14
1946, Due west.F. Libby estimated that the average global product rate of carbon-14 was sufficient to observe it in natural samples
1947, Anderson demonstrated the presence of carbon-fourteen in methane extracted from sewage gas and suggested its use for dating biological samples
1949, Arnold and Libby demonstrated the feasibility of the carbon-14 method of dating past analysing archeological samples of known age
1952, Libby published his famous book "Radiocarbon Dating", and was awarded the Nobel Prize for Chemistry in 1960