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  • Created by: Rianne B
  • Created on: 20-04-13 13:13


The spontaneous decay of an unstable nucleus by the emission of ionising radiation.  It is a random process, so we cannot predict when it will occur.

An atom is a neutral particle because it contains equal numbers of protons and electrons.  The nucleus of an atom contains two types of sub-atomic particles which are protons and neutrons.  Electrons are in shells on the outside of the atom and affect chemical properties. 


Same bumber of protons and a different number of neutrons.  Radioisotopes are different forms of an element with the same number of protons but different bumbers of neutrons and are unstable and decay by emitting ionising radiation. 

Properties of Radiation

There are three types of radiation:

Alpha Particles

An alpha particle is


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