Physics

The Columbia Encyclopedia,... World Encyclopedia The Oxford Pocket Dictionary... A Dictionary of Astronomy Further reading

proton

The Columbia Encyclopedia, 6th ed. | 2011 | Copyright

proton elementary particle having a single positive electrical charge and constituting the nucleus of the ordinary hydrogen atom. The positive charge of the nucleus of any atom is due to its protons. Every atomic nucleus contains one or more protons; the number of protons, called the atomic number, is different for every element (see periodic table ). The mass of the proton is about 1,840 times the mass of the electron and slightly less than the mass of the neutron . The total number of nucleons, as protons and neutrons are collectively called, in any nucleus is the mass number of the nucleus. The existence of the nucleus was postulated by Ernest Rutherford in 1911 to explain his experiments on the scattering of alpha particles; in 1919 he discovered the proton as a product of the disintegration of the atomic nucleus. The proton and the neutron are regarded as two aspects or states of a single entity, the nucleon. The proton is the lightest of the baryon class of elementary particles . The proton and other baryons are composed of triplets of the elementary particle called the quark. A proton, for instance, consists of two quarks called up and one quark called down, a neutron consists of two down quarks and an up quark. The antiparticle of the proton, the antiproton, was discovered in 1955; it has the same mass as the proton but a unit negative charge and opposite magnetic moment. Protons are frequently used in a particle accelerator as either the bombarding (accelerated) particle, the target nucleus, or both. The possibility that the proton may have a finite lifetime has recently come under examination. If the proton does indeed decay into lighter products, however, it takes an extremely long time to do so; experimental evidence suggests that the proton has a lifetime of at least 10 ³¹ years.

Cite this article
Pick a style below, and copy the text for your bibliography.

MLA
Chicago
APA

"proton." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>.

"proton." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1E1-proton.html

"proton." The Columbia Encyclopedia, 6th ed.. 2011. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1E1-proton.html

Learn more about citation styles

proton

World Encyclopedia | 2005 | Copyright

proton (symbol p) Stable elementary particle with a positive charge equal in magnitude to the negative charge of the electron. The proton was discovered (1919) by Ernest Rutherford. It forms the nucleus of the lightest isotope of hydrogen and, with the neutron, is a constituent of the nuclei of all other elements. It is made up of three quarks. The proton is a baryon with a mass c.1836 times heavier than the electron. The number of protons in the nucleus of an element is equal to its atomic number. Protons also occur in primary cosmic radiation. Beams of high-velocity protons, produced by particle accelerator, are used to study nuclear reactions. See also particle physics

Cite this article
Pick a style below, and copy the text for your bibliography.

MLA
Chicago
APA

"proton." World Encyclopedia. 2005. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>.

"proton." World Encyclopedia. 2005. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O142-proton.html

"proton." World Encyclopedia. 2005. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O142-proton.html

Learn more about citation styles

proton

The Oxford Pocket Dictionary of Current English | 2009 | Copyright

pro·ton / ˈprōˌtän/ • n. Physics a stable subatomic particle occurring in all atomic nuclei, with a positive electric charge equal in magnitude to that of an electron, but of opposite sign. DERIVATIVES: pro·ton·ic / prōˈtänik/ adj.

Cite this article
Pick a style below, and copy the text for your bibliography.

MLA
Chicago
APA

"proton." The Oxford Pocket Dictionary of Current English. 2009. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>.

"proton." The Oxford Pocket Dictionary of Current English. 2009. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O999-proton.html

"proton." The Oxford Pocket Dictionary of Current English. 2009. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O999-proton.html

Learn more about citation styles

proton

A Dictionary of Astronomy | 1997 | Copyright

proton An elementary particle that has a positive charge, equal and opposite to that of the electron. It is a hadron, with a rest mass of 1.673 × 10^-27 kg, which is 1836.15 times that of the electron. It is present in the nuclei of all atoms; the hydrogen nucleus is a single proton.

Cite this article
Pick a style below, and copy the text for your bibliography.

MLA
Chicago
APA

"proton." A Dictionary of Astronomy. 1997. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>.

"proton." A Dictionary of Astronomy. 1997. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O80-proton.html

"proton." A Dictionary of Astronomy. 1997. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O80-proton.html

Learn more about citation styles

proton

The Concise Oxford Dictionary of English Etymology | 1996 | | Copyright

proton (phys.) unit of matter associated with a charge of positive electricity. XX. — n. sg. of Gr. prôtos first.

Cite this article
Pick a style below, and copy the text for your bibliography.

MLA
Chicago
APA

T. F. HOAD. "proton." The Concise Oxford Dictionary of English Etymology. 1996. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>.

T. F. HOAD. "proton." The Concise Oxford Dictionary of English Etymology. 1996. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O27-proton.html

T. F. HOAD. "proton." The Concise Oxford Dictionary of English Etymology. 1996. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O27-proton.html

Learn more about citation styles

proton

Oxford Dictionary of Rhymes | 2007 | Copyright

proton •Agamemnon, Memnon •ninon, xenon •noumenon • Trianon • xoanon •organon • Simenon • Maintenon •crampon, kampong, tampon •Nippon • coupon •Akron, Dacron, macron •electron • natron • Hebron • positron •Heilbronn • micron •boron, moron, oxymoron •neutron • interferon •fleuron, Huron, neuron •Oberon • mellotron • aileron •cyclotron • Percheron • Mitterrand •vigneron • croissant • Maupassant •garçon • Cartier-Bresson • exon •frisson • Oxon • chanson • Tucson •soupçon • Aubusson • Besançon •penchant • torchon • cabochon •Anton, canton, Danton •lepton •piton, Teton •krypton • feuilleton • magneton •chiton •photon, proton •croûton, futon •eschaton • peloton • contretemps •telethon •talkathon, walkathon •Avon • tableau vivant • vol-au-vent

Cite this article
Pick a style below, and copy the text for your bibliography.

MLA
Chicago
APA

"proton." Oxford Dictionary of Rhymes. 2007. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>.

"proton." Oxford Dictionary of Rhymes. 2007. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O233-proton.html

"proton." Oxford Dictionary of Rhymes. 2007. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O233-proton.html

Learn more about citation styles

Free newspaper and magazine articles

	Proton pros and cons; Some cite dearth of studies on effectiveness; others... Magazine article from: Modern Healthcare; 9/27/2010
	Proton beam therapy subject of renewed radiosurgical interest. Magazine article from: Medical Device Week; 9/11/2007
	Protons may waltz off nuclear dance floor.(nuclear emissions testing:... Magazine article from: Science News; 10/21/2000