There are 3 basic types of radioactive decay:

Alpha – a particle (a He nucleus) is emitted causing the atomic mass to reduce by 4 (2 neutrons and 2 protons, and the atomic number to be reduced by 2.  View an example of this type of decay.

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Beta – a particle (either a -b or positron +b) is emitted, which is so small that it causes no change in atomic mass. When negatively charged (-b) it causes a neutron to become a proton, increasing the atomic number by 1.  When positively charged (+b) it causes a proton to become a neutron, decreasing the atomic number by 1. View an example of these types of decay.


Gamma – is an energy packet (photon) which has no mass and no charge. It does not change either the atomic mass or atomic number. View an example of this type of decay.


alpha particle beta particle