Alpha Particles
Alpha particles are sometimes referred to as alpha rays or alpha radiation. During the radioactive decay of certain materials, positively charged particles are released.
The mass of an alpha particle consists of two neutrons and two protons; therefore, an alpha particle nucleus is quite similar to a helium-4 nucleus.
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An alpha particle is indicated by the Greek alphabet α.
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Alpha particles have a large mass as they are made up of 4 nucleons and have a mass number of 4.
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They carry two protons, so their relative charge is +2.
The range of ionizing radiation of alpha particles is relatively short:
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These particles can travel only a few centimeters in the air and cannot penetrate more than a few millimeters of paper.
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Alpha particles interact with atoms along their path, giving up energy rapidly, which limits their range.
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Typically, alpha particles have a range of about 5–8 cm in air and are easily stopped by it.
Example of Alpha Decay
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Radium-222, a radioactive element in the periodic table, decays to become the element radon by emitting alpha particles.
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Radon is a radioactive gas that decays further, also releasing alpha particles.
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When a radioactive element undergoes alpha decay, the mass number decreases by 4, and the atomic number decreases by 2 due to the emission of alpha particles.