alpha particle

American  

noun

Physics.

1. a positively charged particle consisting of two protons and two neutrons, emitted in radioactive decay or nuclear fission; the nucleus of a helium atom.

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alpha particle British  

noun

1. a helium-4 nucleus, containing two neutrons and two protons, emitted during some radioactive transformations

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alpha particle Scientific  

1. A positively charged particle that consists of two protons and two neutrons bound together. It is emitted by an atomic nucleus undergoing radioactive decay and is identical to the nucleus of a helium atom. Because of their relatively large mass, alpha particles are the slowest and least penetrating forms of nuclear radiation. They can be stopped by a piece of paper.

2. See more at radioactive decay

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Etymology

Origin of alpha particle

First recorded in 1900–05

Example Sentences

When astatine decays, it emits alpha particles -- tiny clusters made of two protons and two neutrons -- that can release powerful, localized bursts of energy.

From Science Daily

The experiment involved bombarding a thin sheet of gold foil with alpha particles, and earned Rutherford, from Bridgewater on New Zealand's South Island, the moniker the "father of nuclear physics".

From BBC

It took 23 measurements with an instrument called an alpha particle X-ray spectrometer.

From BBC

But without a spin, researchers of the Physics Review D paper suggest feeding the tiny black hole with charged alpha particles.

From Salon

She'd already begun to establish her reputation as a physicist, working on alpha particle scattering.

From Scientific American