OCR AS Chemistry F331: Radioactive Tracers

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Radioactive Tracers
Because it's easy to detect radiation given out by radioactive isotopes, they're used as
Tracers: radioactive isotopes whose decay is monitored
Medical tracers:
Radioisotopes can be injected into the body to locate problems including cancerous
Iodine-131 is used to detect thyroid problems
Technetium-99 is used to detect tumours
The tracer can also be eaten or drunk and then its pathway is followed using a Geiger
An isotope should have a half-life which is neither:
- too short, which will mean it will decay before the tracing is complete
- too long, which could cause harm to the patient's body
Generally, radioisotopes used as tracers should be gamma emitters ­ enabling
detection and minimising ionisation of cells.
Radioisotopes can cause cancer, but tracers are relatively safe.
Small doses are used to limit exposure.
The benefits of early diagnosis are considered to outweigh the risks.

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Uses of Radioisotopes in Geology
The fact that some types of mineral in certain rock types contain radioactive elements offers
the potential to estimate the age of the host rock.
They can be used a geological rocks.
If the origin, or parent, radioisotope decays through a series of daughter products to
eventually form a stable non-radioactive isotope of an element then it may be
possible to estimate the age of the rock by working out the mass ratio of parent to
final daughter product.…read more

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Uses of Radioisotopes in Archaeology
Radiocarbon Dating
The carbon-14 isotope occurs naturally and is present along with the carbon-12 isotope in
all living things.
The ratio of carbon-12 to carbon-14 does not change in a living organism, but when
an organism dies the carbon-14 is not replenished and the ratio of carbon-12 to carbon-
14 gradually increases.
If this ratio can be measured it can give an estimate of the age of the material since it
died.…read more


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