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Carbon dating is a method of determining the age of an organic material with the help of radiocarbon (also known as isotopic chronometer). This carbon 14 isotope is one of the weakest radioactive isotopes of carbon which is used in this method. Accelerator mass spectrometry and gas proportional counting are the two types of carbon dating.
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Key Terms: Carbon Dating, Isotope, Organic, Principle, Radiocarbon, Radioisotope, Spectrometry, Accelerator, Nitrogen, Atoms, Cosmic rays
What is Carbon Dating?
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Carbon Dating is defined as a method to determine the speculative age of an organic and some inorganic materials (except metals) from a living organism using properties of radiocarbon. This could be measured by the amount of carbon-14 in the organic material with reference to an international standard. It is one of the most important discoveries made by Willard Libby in the 20th century.
From the past several years carbon dating technique has been used in various disciplines such as geology, atmospheric science, geophysics and oceanography etc. The radioactive isotopes of carbon are constantly being developed on earth, when cosmic rays coming from the organic material interact with atmospheric nitrogen. The radioactive molecules decay on a specific rate on the basis of mass and the atomic number of the decayed atoms.
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Principle of Carbon Dating
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The radiocarbon C-14 is an unstable and weakly radioactive isotope of carbon. The radioactive carbon is developed in the upper atmosphere of earth due to the interactions of cosmic rays with the nitrogen atoms. The resultant compound quickly oxidises in the atmosphere to form a radioactive carbon dioxide and enters into the carbon cycle.
Organisms present on earth then assimilate the resultant carbon 14 isotope through both photosynthesis and eating. When the living organisms die, their body stops exchanging the carbon with the biosphere, which results in the decreasing rate of radioactive decay of carbon 14 isotope.
Importance of Carbon Dating
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Radiocarbon dating has been used in speculating the age of decaying materials. Without this discovery it would have been very difficult to determine the age of an organic material. It is important as:
- Carbon dating is a revolutionary concept in the study of our planet's history. It leads to the restructuring of the history of our world.
- It allows scientists to learn about the past civilizations, extinct species like dinosaurs, fossil fuels, changes in earth and its climates.
- It is one of the significant developments in archaeology which helps in determining the substance's age.
Measurement of Radioactive Carbon
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There are usually two different methods which are used in calculating the carbon 14 isotope from any given organic material, which are:
- Gas Proportional Counting: It is the most basic radiometric dating method. It counts the number of beta particles emitted by the radiocarbon decay of an organic material.
- Accelerator mass spectrometry: This is the most efficient method of measuring the radiocarbon content of a material. The carbon 14 isotope is calculated in reference to its other two isotopes. It counts the number of carbon atoms present in the material and their proportion.
Things to Remember
- Age of a radiocarbon isotope can be analysed by estimating its carbon 14 substance and in comparison with the result of carbon 14 activity in modern samples.
- It is continuously created by the interactions of cosmic rays with the atmospheric nitrogen.
- Carbon 14 isotope has half life period of 5,730 years.
- Liquid scintillation counting, gas proportional counting and accelerator mass spectrometry are three methods of radiocarbon dating.
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Sample Questions
Ques. What is carbon dating and how does it work? (2 Marks)
Ans. The basis of radioactive carbon dating is simple in which all living things assimilate carbon from the environment and food resources around them, including a specific measure of natural, radioactive carbon-14. When the living organisms dies, their body stops exchanging the carbon with the biosphere which results in the decreasing rate of radioactive decay of carbon 14 isotope.
Ques. How is carbon dating done? (2 Marks)
Ans. Radiocarbon dating works by looking at the three different isotopes of carbon. Isotopes of a specific component have a similar number of protons in their nucleus, but different numbers of neutrons. Carbon 14 interacts with neutrons created by cosmic rays with nitrogen 14 molecules.
Ques. What is an example of carbon dating? (2 Marks)
Ans. The carbon dating can be used in any organic material for determining their ages such as charcoal, peat, lake mud, wall paintings, corals, soil, hair, wood, twigs, seeds, bones, shells, leather, pottery, pollen, blood residues and fabrics.
Ques. What do you mean by an activity in a radioactive substance? Write its SI unit? (2 Marks)
Ans. The rate of disintegration that takes place in a radioactive substance is known as activity. The SI unit of an activity is Becquerel.
Ques. What do you mean by radioactive disintegration of radioactive material? (1 Mark)
Ans. The process of conversion of one radioactive nuclei into another nuclei with the emission of alpha, beta and gamma rays is known as radioactive disintegration.
Ques. What is a radioactive dating method? (2 Marks)
Ans. Radioactive dating is a technique for speculating the age of rocks and minerals by using radioactive isotopes. This method is good for igneous and metamorphic rocks, which can't be dated by the use of stratigraphic connection strategy, which is used for sedimentary rocks.
Ques. What describes a radioisotope? (2 Marks)
Ans. The radioactive isotope of an element is known as radioisotope. It is an atom which consists of an unstable combination of neutrons and protons, or excess energy in their nucleus.
Ques. What is accelerator mass spectrometry in carbon dating? (2 Marks)
Ans. This is the most efficient method of measuring the radiocarbon content of a material. In this method, carbon 14 is directly compared with carbon 12 and carbon 13 present in that material. It counts the quantity of carbon atoms present in the sample and the extent of the isotopes.
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