Half life and decay series (3.4) Flashcards
What is the half-life of a radioisotope
The half-life (t 1/2) of a radioisotope is the time taken for half of the nuclei of the sample radioisotope to decay
Behaviours of large samples of radioisotopes can be mathematically predicted, behaviours of smaller samples cannot be predicted (NA)
The half life of a radioisotope is constant and cannot be altered by chemical reactions (NA)
What is a geiger counter used for?
A geiger counter can be used to record the number of decays occurring in a sample per second - It measures the activity of the sample.
The equation for number of nuclei after a number of half lives can also be used to calculate the final activity of a radioactive sample safer a number of half lives (NA)
What determines how/what a radioisotope is used for?
The half life of a radioisotope will determine what It is used for (NA)
Give an example of a radioisotope used for it’s short half life
Technetium-99 is used has a half life of 6 hrs and used as a medical tracer. The short half life ensures the body isn’t exposed to radiation longer than it has to be
Give an example of a radioisotope used for it’s long half life
Americium-241 has a half life of 461 years. Used in smoke detectors, as long as batteries are changed yearly , the detector will work in the event of a fire
What is a decay series
Decay series sequences of radioactive daughter nuclei that are formed by the radioactive decay of a parent nuclide to a final stable daughter nuclide.
Difference between nucleus, nuclides and nucleons
Nuclide is a nucleus characterised by a specific number of protons and neutrons
Nucleons are the protons and neutrons that inhibit the nucleus
Nucleus is the central part of the atom which contains the atoms mass + protons and neutrons
Describe Radiocarbon Dating
Is the technique used by archaeologists to determine the ages of fossils and ancient objects by measuring and comparing proportions of carbon-12 and carbon-14
Describe how Radiocarbon Dating works
Carbon-14 is radioactive and Carbon-12 is stable.
When an organism dies, the carbon-14 in the body will decay to form nitrogen 14 and thus decrease in particle quantities. As carbon-12 is stable, its numbers does not change. Therefore by comparing the proportion of Carbon-12 and Carbon-14 in a living organism to the fossil, the age of the fossil can be determined.
