A box full of radiation ( continued )
YEARS 7 – 12 IDEAS FOR THE CLASSROOM
A box full of radiation ( continued )
Nuclei too big
α
Too many neutrons
Beta-radiation
That leaves two boxes and one type of radiation that has not been used yet . There is a variety of ways to come to the right decision ( for example , you could simply tell the students ) but I like getting the class to vote on it , overthrowing the vote if it is wrong .
Too few neutrons |
Too much energy |
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Nuclei too big |
Too many neutrons |
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α |
β |
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Too few neutrons |
Too much energy |
Nuclear equations
At this point I introduce nuclear equations . Alpha-decay is pretty easy for students to get . I also introduce the decay of uranium-238 , as I can connect it later to the uranium decay series .
γ
Gamma-radiation
Next I encourage the connection between too much energy and gamma radiation , which most students are quick to jump to .
The example I like to give is the decay of molybdenum to get to technetium-99m . This again can lead to a discussion about the production of medical isotopes in nuclear reactors , like the reactor at ANSTO .
Nuclei too big
α
Too many neutrons Extension – neutron decay : at this point I like to explain how beta-radiation works , at least at a simple level . I try to get the students to form the nuclear equation :
(+ anti-neutrino )
Too few neutrons
Too much energy
I introduce the example of technetium-99m , which is used routinely as a medical isotope in Australia and a good segue to talking about ANSTO and Lucas Heights . γ
Extension – decay series : now that the students have the basic tools of alpha- and beta-decay , I like to introduce the decay series of uranium-238 , showing the battle between the nucleus being too big and the nucleus having too many neutrons .
Extension – half-lives and uranium : lead dating : following on from the decay series , it can be fun to investigate the half-lives of each step in the series . The discussion can be turned around to the dating of the age of the Earth , and how the decay of uranium can be used . A more probing question is why they use the ratio of uranium to lead and not the ratio of uranium to thorium .
Extension – the fourth box : this box is often ignored but has the weirdest and most interesting stuff going on . First of all , if the
56 SCIENCE EDUCATIONAL NEWS VOL 66 NO 4