Radioactivity Notes

Heres what you need to know about from the chapter entitled ” Radioactivity”

History: Henri Bequerel discovered radiation accidentally when he left some photographic plates in his drawer with some uranium salt. The plate changed-something was invisibly coming from the uranium. His pals Pierre and Marie Curie isolated polonium and radium. Radiation is actually all around us like radon gas. Sometimes is dangerous though.

Definition: Radioactivity is the spontanoeus breaking up of unstable nuclei with the emission of one or more types of radiation.

Info Alpha Beta Gamma
Nature helium nucleus. an electron electromagnetic wave.high frequency.
Why released? this 2p2n nucleus is spit out to change an unstable nucleus to a stable one neutron in the nucleus changes into proton and electron. electron is spit out as beta nucleus wants to lose surplus energy
Affected by? electric fields. attracted towards negative plate.2+charge electric fields.attrac. to posotive plates. -1charge nothing far as your concerned. isnt deflected
Penetrating power paper 5mm alluminium several cm lead
Examples/Emitted by: Americium 241-smoke detectors Carbon 14-dating cobalt 60-cancer treatmen

Nuclear Reactions

As the name suggests – you only concentrate on what is in the nucleus. The electrons dont matter. One element changes into another here if not two.
Here is how the release of particles affects the nuclei-we only look here at alpha and beta emission because gamma does not change the nucleus:

Mass Number Atomic Number
Goes down by 4 Goes down by two Alpha
Dosent change(neutron–>proton + electron) Goes up by one Beta

Half Life: the half life of an element is the time taken for half of the nuclei in any given sample to decay.

* A Geiger Muller tube and ratemeter is used to measure it.
* Count rate example : 400 and 30 minutes later 200. that means half life is 30 minutes long.

Uses of Radiation: NB: you only need to know 3:

* Medical: Gamma is used to kill cancer. Sterelise.
* Archeological : Carbon 14 dating
* Food: Irradation-kills bacteria on food without losing taste
* War: guess


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