alpha particle

noun

Definition of alpha particle

: 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

Examples of alpha particle in a Sentence

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, "Health," 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, "Where Does the Oxygen in the Universe Come From, Exactly?," 21 Aug. 2019 Hoyle state nuclei almost always decay right back into beryllium and an alpha particle. Quanta Magazine, "A Primordial Nucleus Behind the Elements of Life," 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, "A Primordial Nucleus Behind the Elements of Life," 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, "The New Science of the Sun Will Be Astounding—And Possibly Terrifying," 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, "Police looking for shooter after one injured in Keizer," 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, "Blowing in the wind: Plutonium at former nuclear weapons site," 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, "How the nerve agent in the spy attack and other toxins cause widespread contamination," 24 Mar. 2018

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.

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First Known Use of alpha particle

1903, in the meaning defined above

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The first known use of alpha particle was in 1903

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Cite this Entry

“Alpha particle.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/alpha%20particle. Accessed 30 Sep. 2020.

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More Definitions for alpha particle

alpha particle

noun

Medical Definition of alpha particle

: 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

More from Merriam-Webster on alpha particle

Britannica.com: Encyclopedia article about alpha particle

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