The half life of a radioactive substance is the time taken for the substance to half in radioactivity e.g. 3hours for the counts per minute to drop from 200 to 100
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Alpha, Beta and Gamma.. what are they?
Alpha is a helium nucleus
Beta is fast moving electrons
Gamma is an electromagnetic wave
Penetrative Properties
Alpha is the least penetrative. It can be stopped by a piece of paper
Beta can penetrate air and paper but is stopped by thin metal
Gamma can penetrate thin metal but is stopped by thick lead
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Isotopes
All the atoms of a given element have the same number of protons and electrons. However, the number of neutrons can vary. Atoms of the same element that have different numbers of neutrons are called isotopes of that element
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