alpha particle

noun

: a positively charged nuclear particle identical with the nucleus of a helium atom that consists of two protons and two neutrons and is ejected at high speed in certain radioactive transformations

called also alpha, alpha radiation, alpha ray

Example Sentences

Recent Examples on the Web The fourth decay can occur by two different routes, with each path releasing one alpha particle and one beta particle before reaching lead-209. Jacqueline Detwiler, Popular Mechanics, 1 Feb. 2020 Starting with oxygen gas, the team will split its nucleus into a helium nucleus, also known as an alpha particle, and a carbon-12 nucleus. David Grossman, Popular Mechanics, 21 Aug. 2019 Hoyle state nuclei almost always decay right back into beryllium and an alpha particle. Quanta Magazine, 4 Dec. 2012 Like a bent arm, the Hoyle state takes the shape of an obtuse triangle with an alpha particle at each vertex. Quanta Magazine, 4 Dec. 2012 These particles, primarily composed of electrons, protons, and helium nuclei (known as alpha particles), fly all over the solar system. Jay Bennett, Popular Mechanics, 9 Aug. 2018 But unlike cosmic radiation or radon gas, plutonium can lodge itself inside the body and deliver tissue-damaging alpha particles over a lifetime. Ted Sickinger, OregonLive.com, 22 Apr. 2018 But unlike cosmic radiation or radon gas, plutonium can lodge itself inside the body and deliver tissue damaging alpha particles over a lifetime. Ralph Vartabedian, latimes.com, 16 Apr. 2018 Polonium-210 has a half-life of 139 days, meaning after this time half of its atoms have emitted an alpha particle and decayed into polonium-206 atoms. Vera Thoss, Washington Post, 24 Mar. 2018 See More

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'alpha particle.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

Word History

First Known Use

1903, in the meaning defined above

Time Traveler
The first known use of alpha particle was in 1903

Dictionary Entries Near alpha particle

Cite this Entry

“Alpha particle.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/alpha%20particle. Accessed 3 Dec. 2022.

Kids Definition

alpha particle

noun

: a positively charged particle that is identical with the nucleus of a helium atom, consists of 2 protons and 2 neutrons, and is thrown at high speed from a radioactive atomic nucleus

Medical Definition

alpha particle

noun

: a positively charged nuclear particle identical with the nucleus of a helium atom that consists of two protons and two neutrons and is ejected at high speed in certain radioactive transformations

called also alpha, alpha ray

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