Radioactivity

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by vjosie
Last updated 5 years ago

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Science
Subject:
Physics
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Radioactivity

Radioactive isotope element:CARBON

Carbon has 15 known isotopes;8Carbon9Carbon10Carbon11Carbon (most stable with half-life of 20.334 minutes)12Carbon (stable naturally occurring)13Carbon (stable naturally occurring)14Carbon (naturally occurring longest radioisotope, with a half-life of 5,700 years)15Carbon16Carbon17Carbon18Carbon19Carbon20Carbon21Carbon22Carbon

The special thing about 14C is that it decays by very weak beta decay, which has to do with electron emissions to nitrogen-14. The carbon-14 method has proved to be an adaptable technique of dating fossils and archaeological specimens from 500 to 50,000 years old. The method is widely used by Pleistocene geologists, anthropologists, archaeologists, and investigators in related fields.

All other radioisotopes have half-lives less than 20 seconds, most less than 200 milliseconds. The least stable isotope is 8C, with a half-life of 2.0 x 10−21 s. Carbon was first discovered as charcoal in prehistoric times. Carbon wasn't recognized as an element until the seventeenth century, after Robert Boyle suggested that an element was a substance that could not be decomposed into simpler substances.

Radiocarbon datingCarbon-14 is a radioactive isotope used to date organic material. This process is called radiocarbon dating. Its consistent rate of decay allows the age of an object to be determined by the proportion of carbon-14 to other carbon isotopes. Carbon dating works by comparing the amount of carbon-14 in a sample to the amount of carbon-12. Because organisms stop taking in carbon-14 at death, the age of the material can be precisely determined by this ratio of carbon isotopes. Carbon-14 is also used as a radioactive tracer for medical tests.

APPLICATIONS AND USES

Nuclear MedicineCarbon-14 is used in studying abnormalities of metabolism that underlie diabetes, gout, anaemia, and acromegaly. Various scanning devices and techniques have been developed, including tomography and magnetic resonance imaging.Radioactive carbon-14 determines the number of fat cells remains constant in all body types. Bruce Buchholz (scientist from Humboldt University Berlin) applied carbon dating to DNA to discover that the number of fat cells stays constant in adulthood in lean and obese individuals, even after marked weight loss. This indicated that the number of fat cells is set during childhood and adolescence. Carbon dating is typically used in archaeology and palaeontology to date the age of artefacts, however, in this application, the scientists used the pulse of radiocarbon to analyse fat cell turnover in humans.

Justify why this particular isotope is used, referring to its half-life and other valuable properties

On February 27, 1940, two chemists, Martin Kamen and Samuel Ruben, realized that the basic element of carbon had a radioactive isotope. It is known as “carbon-14” because it has two additional neutrons. The ion (an atom or molecule in which the total number of electrons is not equal to the total number of protons) exists in all sorts of natural organisms and can be used to estimate the age of materials up to 50,000 years old. Willard Libby, (1946) a chemist at the University of Chicago, experimented with carbon-14 further. Through a series of tests, he calculated the atom’s half-life to be approximately 5,568 years, slightly less than the currently accepted measurement (5,730 years) discovered at Cambridge University in 1962. He theorized that, by analysing the amount of carbon-14 in plant matter, an estimation of the item’s age could be formed.

DECAY PROCESS AND HALF-LIFE RESULT Carbon-14 goes through radioactive beta decay: By emitting an electron and an electron antineutrino, one of the neutrons in the carbon-14 atom decays to a proton and the carbon-14 (half-life of 5730 years) decays into the stable (non-radioactive) isotope nitrogen-14. Carbon-14 decays by emitting beta particles and giving nitrogen. 146C → 147N + β-particle(e-). Carbon-14 has a relatively short half-life of 5,730 years, meaning that the fraction of carbon-14 in a sample is halved over the course of 5,730 years due to radioactive decay to nitrogen-14. The carbon-14 isotope would vanish from Earth's atmosphere in less than a million years were it not for the constant influx of cosmic rays interacting with molecules of nitrogen (N2) and single nitrogen atoms (N) in the stratosphere. Both processes of formation and decay of carbon-14 are shown in the image below.

Carbon14 is produced as a secondary effect of a constant cosmic ray bombarding the upper atmosphere. The carbon14 level is always maintained constant because of the metabolic processes of the living organisms. The living organisms naturally abide in this carbon filled environment and once it dies it is automatically removed from this environment. Then the organism will then start to lose a certain amount of 14C. It is decreased by a function of its half-life. The 14C age determination is based on the measurement of the residual 14C activity in a sample compared to the activity of a sample of an assumed zero ago from the same environment and era. Furthermore, the accuracy of the radiocarbon determination are from the production of 14C by cosmic rays they need to be constantly long enough to establish a steady state.

PMI CHARTPOSITIVE-Carbon-14 (C-14) dating is a way of determining the age of certain archaeological artefacts of a biological origin up to about 50,000 years old. It is used in dating things such as bone, cloth, wood and plant fibres that were created in the relatively recent past by human activities.-Naturally occurring C-14 is in the food we eat and the air that we breathe and represents no threat to our health. There is radiation all around us from Carbon-14 and other sources. The harm it causes in our cells is low; our bodies are used to it and are able to repair the damage.NEGATIVE-The most common problem with carbon decay is that the carbon containing compounds are physically or chemically introduced to the sample resulting in a contamination.-C-14 dating becomes less accurate over about 50,000 years and it should not be used to date items over about 100,000 years old.- Large amounts of carbon 14 were also released to the atmosphere as a result of nuclear weapons testing. It can enter the body through inhalation, contaminated drinking water, or contaminated food. The health hazard of carbon 14 is associated with cell damage caused by the ionizing radiation that results from radioactive decay, with the potential for subsequent cancers.INTERESTING-Carbon occurs naturally as carbon-12, which makes up almost 99% of the carbon in the universe. Carbon-13 makes up about 1%. Carbon-14 makes up a very tiny amount of overall carbon but is very important in dating organic objects.


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