| When alpha particles, beta particles or gamma rays collide with atoms of an absorbing material, electrons are torn from the atoms. As a result, the atoms become positively charged. The positively charged atoms and the negatively charged electrons are referred to as "ions". The charged atom is a positive ion and the negatively charged electron is a negative ion. This process is called ionisation. Energy is transferred to the absorber during the ionisation process. For a given thickness of absorber, alpha radiation produces the most ionisation, beta next and gamma least. [ This page has been adapted from www.bbc.co.uk/schools/gcsebitesize/science
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