1) The nucleus of a helium atom
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(
42He) A particle that is commonly ejected from radioactive nuclei, consisting of two protons and two neutrons. Alpha particles are helium nuclei. Alpha particles have a mass of 6.644 655 98 × 10
-27 kg or 4.001 506 1747 atomic mass units. [1998 CODATA values]
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http://antoine.frostburg.edu/chem/senese/101/glossary/a.shtml
A Helium nucleus consisting of two protons and two neutrons, generally seen as a decay product from a heavy radioactive nucleus.
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http://www-bdnew.fnal.gov/operations/accgloss/gloss.html#A
positively charged particle, identical to the nucleus of the helium-4 atom, spontaneously emitted by some radioactive substances, consisting of two ... [24 related articles]
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http://www.britannica.com/eb/a-z/a/52
A helium nucleus.
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http://www.chemistry-dictionary.com/definition/alpha+particle.php
Ionising radiation produced from the spontaneous decay of certain radioactive materials. An alpha particle consists of the nucleus of a Helium atom. Alpha particles are easily stopped by tissue or other material; therefore damage only occurs to tissue close to the radiation source.
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helium 4 atomic nucleus emitted during a nuclear disintegration
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http://www.electropedia.org/iev/iev.nsf/display?openform&ievref=393-11-31
a stable particle having the same bound configuration of 2 protons and 2 neutrons as a helium-4 nucleus, emitted during nuclear disintegration
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A particle emitted by a radionuclide consisting of two protons plus two neutrons.
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http://www.encyclo.co.uk/local/20474
A positively-charged particle from the nucleus of an atom, emitted during radioactive decay. Alpha particles are helium nuclei, with 2 protons and 2 neutrons
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http://www.encyclo.co.uk/local/20725
A positively charged particle from the nucleus of an atom, emitted during radioactive decay. An alpha particle is a helium nucleus made up of two protons and two neutrons.
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http://www.encyclo.co.uk/local/20841
<physics> A radioactive particle made up of two protons and two neutrons, these particles are created by the decay of a radioactive material or by nuclear bombardment, and they are the same as the nucleus of a helium-4 atom. ... (09 Oct 1997) ...
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http://www.encyclo.co.uk/local/20973
A positively-charged particle from the nucleus of an atom, emitted during radioactive decay.
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http://www.encyclo.co.uk/local/21076
the nucleus of a helium atom, made up of two neutrons and two protons with a charge of +2. Certain radioactive nuclei emit alpha particles. Alpha particles generally carry more energy than gamma or beta particles, and deposit that energy very quickly while passing through tissue. Alpha particles can be stopped by a thin layer of light material, su...
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A positively-charged particle from the nucleus of an atom, emitted during radioactive decay. Alpha particles are helium nuclei, with 2 protons and 2 neutrons. ...
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A positively charged particle consisting of two Neutrons and two protons which is emitted from Atoms undergoing Alpha Decay . The range of the alpha particle is short (a few cm's in air) and they are easily shielded (stopped by a single sheet of paper). They only present a significant hazard where they enter the body - even the most energetic ...
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http://www.ionactive.co.uk/glossary_atoz.html?s=az&t=a
(α) Type: Term Definitions: 1. a particle consisting of two neutrons and two protons, with a positive charge (2e+); emitted energetically from the nuclei of unstable isotopes of high atomic number (elements of mass number from 82 up); identical to the helium nucleus. Synonyms: alpha ray
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http://www.medilexicon.com/medicaldictionary.php?t=66069
Alpha particle: A tiny mass of material composed of two protons and two neutrons. Alpha particles do not travel very far from their radioactive source. They cannot pass through a piece of paper, clothes or even the layer of dead cells which normally protects the skin. Because alpha particles cannot penetrate human skin they are not considered an 'e...
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http://www.medterms.com/script/main/art.asp?articlekey=9642
Particle of matter that is positively charged. This particle consists of two neutrons and two protons and is emitted as a form of radioactivity from the nuclei of some radioisotopes. Also see beta particle and gamma rays.
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http://www.physicalgeography.net/physgeoglos/a.html
noun a positively charged particle that is the nucleus of the helium atom; emitted from natural or radioactive isotopes
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https://www.encyclo.co.uk/local/20974
Positively charged (2+), high-energy particle emitted from the nucleus of a radioactive atom. It is one of the products of the spontaneous disintegration of radioactive elements (see radioactivity) such as radium and thorium, and is identical to the nucleus of a helium atom (
4He) – that is, it consists of two pro...
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https://www.encyclo.co.uk/local/21221
A particle consisting of two protons and two neutrons, produced during alpha decay. Identical to the nucleus of a 4He atom.
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https://www.encyclo.co.uk/local/22327
a cluster of 2 protons and 2 neutrons emitted from a nucleus in one type of radioactivity.
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https://www.encyclo.co.uk/local/22434
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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https://www.infoplease.com/dictionary/alpha-particle
A positively-charged particle emitted from the nucleus of an atom during radioactive decay. Alpha particles are helium nuclei, with 2 protons and 2 neutrons.
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https://www.world-nuclear.org/nuclear-basics/glossary.aspx
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