Beta particle is an electron emitted by a nucleus, by the conversion of a neutron into a proton. Gamma rays are electromagnetic radiation emitted by an excited nucleus, where as x-rays are emitted by the excited electrons.
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Alpha particles consist of two protons and two neutrons bound together into a particle identical to a helium nucleus. They have a net spin of zero, and normally a total energy of about 5 MeV. They are a highly ionizing form of particle radiation, and have low penetration.
Gamma rays are electromagnetic radiation of high energy. They are produced by sub-atomic particle interactions, such as electron-positron annihilation, neutral pion decay, radioactive decay, fusion, fission or inverse Compton scattering in astrophysical processes. Gamma rays typically have frequencies above 1019 Hz and therefore energies above 100 keV and wavelength less than 10 picometers, often smaller than an atom. Gamma radioactive decay photons commonly have energies of a few hundred KeV, and are almost always less than 10 MeV in energy.