Alpha particles are helium nuclei, consisting of 2 protons and 2 neutrons. They have a charge of +2e and an atomic mass value of 4 u. Beta particles are either electrons or positrons. They have a charge of –e or +e, respectively. They are about 8000 times less massive than alpha particles. Gamma rays are photons, high-energy quanta of electromagnetic radiation. They have no charge and no mass.
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Gamma radiation is an EM wave of photons and as such it is extremely difficult to block. Alpha particles are helium nuclei with a greater mass and stronger charge, making them easy to deflect; They do not even penetrate human skin. Beta particles fall in between.