alpha particle(redirected from Helium nucleus)
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A positively charged subatomic particle, composed of two protons and two neutrons, identical with the nucleus of the helium isotope He-4.
(General Physics) a helium-4 nucleus, containing two neutrons and two protons, emitted during some radioactive transformations
a positively charged particle consisting of two protons and two neutrons, emitted in radioactive decay or nuclear fission; the nucleus of a helium atom.
A positively charged particle that consists of two protons and two neutrons bound together. It is emitted by the nucleus of some elements undergoing radioactive decay and is identical to the nucleus of a helium atom. Alpha particles are the slowest and least penetrating forms of nuclear radiation. ♦ The process by which a radioactive element emits an alpha particle is called alpha decay. Alpha decay results in the atomic number of the atom being decreased by two and the mass number being decreased by four. See more at radiation, radioactive decay.
A helium nucleus that has a positive electric charge.