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