alpha particle

noun Physics.

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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earnest
full seriousness, as of intention or purpose.
a feeling of dread, anxiety, or anguish.
urgent character; imperativeness; insistence; importunateness.
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Origin of alpha particle

First recorded in 1900–05

Words nearby alpha particle

alpha globulin, alpha granule, alpha helix, alpha iron, alpha male, alpha particle, alpha privative, alpha radiation, alpha ray, alpha receptor, alpha rhythm
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2020

British Dictionary definitions for alpha particle

alpha particle

noun

a helium-4 nucleus, containing two neutrons and two protons, emitted during some radioactive transformations
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Medical definitions for alpha particle

alpha particle

n.

A positively charged nuclear particle, indistinguishable from a helium atom nucleus and consisting of two protons and two neutrons.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Scientific definitions for alpha particle

alpha particle

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. See more at radioactive decay.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.