# Alpha decay

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Alpha decay is a type of radioactive decay in which an atomic nucleus becomes a new more stable atomic nucleus by emitting an alpha particle, which is the nucleus of a helium atom.

${\displaystyle {}_{2}^{4}{\hbox{He}}^{2+}}$

Alpha radiation has the least penetration power of all the primary types of radiation because the alpha particle is both larger, more massive, and more heavily charged then an electron or gamma ray.

## Trivia

• Many smoke detectors use alpha particles to ionize the air, if smoke enters the chamber it absorbs the alpha particles and interrupts the current.
• In addition to being one of the primary forms of radiation alpha particles are also one of the primary sources of helium on earth.