AskDefine | Define proton

Dictionary Definition

proton n : a stable particle with positive charge equal to the negative charge of an electron

User Contributed Dictionary

see Proton



  • italbrac RP /ˈprəʊ.tɒn/
  • italbrac US /ˈproʊ.tɑːn/




  1. A positively charged subatomic particle forming part of the nucleus of an atom and determining the atomic number of an element; the nucleus of the most common isotope of hydrogen; composed of two up quarks and a down antiquark



positively charged nucleon
  • Breton: proton (collective noun), protonenn (singular f)
  • Catalan: protó
  • Cantonese: 質子 (jat1 ji2)
  • Chinese: 質子 (zhí zí)
  • Croatian: proton
  • Czech: proton
  • Danish: proton
  • Dutch: proton
  • Esperanto: protono
  • Finnish: protoni
  • French: proton
  • German: Proton
  • Hungarian: proton
  • Indonesian: proton
  • Icelandic: róteind
  • Interlingua: proton
  • Italian: protone
  • Japanese: 陽子 (ようし, yōshi)
  • Latin: proton, protonis
  • Latvian: protons
  • Norwegian: proton
  • Polish: proton
  • Portuguese: próton
  • Russian: протон (proton)
  • Spanish: protón
  • Swedish: proton
  • Turkish: proton
  • Vietnamese: proton

See also



hr-noun m



  1. proton





Extensive Definition

| magnetic_moment = 2.792847351(28) μN | magnetic_polarizability = | spin = ½ | isospin = ½ | parity = +1 | condensed_symmetries = I(JP) = ½(½+) }}
In physics, the proton (Greek πρώτον / proton = first) is a subatomic particle with an electric charge of one positive fundamental unit (), a diameter of about (0.00000000000000165 metres) , and a mass of (), or about 1836 times the mass of an electron.


Ernest Rutherford is generally credited with the discovery of the proton. In 1918 Rutherford noticed that when alpha particles were shot into nitrogen gas, his scintillation detectors showed the signatures of hydrogen nuclei. Rutherford determined that the only place this hydrogen could have come from was the nitrogen, and therefore nitrogen must contain hydrogen nuclei. He thus suggested that the hydrogen nucleus, which was known to have an atomic number of 1, was an elementary particle. Prior to Rutherford, Eugene Goldstein had observed canal rays, which were composed of positively charged ions. After the discovery of the electron by J.J. Thomson, Goldstein suggested that since the atom is electrically neutral there must be a positively charged particle in the atom and tried to discover it. He used the "canal rays" observed to be moving against the electron flow in cathode ray tubes. After the electron had been removed from particles inside the cathode ray tube they became positively charged and moved towards the cathode. Most of the charged particles passed through the cathode, it being perforated, and produced a glow on the glass. At this point, Goldstein believed that he had discovered the proton. When he calculated the ratio of charge to mass of this new particle (which in case of the electron was found to be the same for every gas that was used in the cathode ray tube) was found to be different when the gases used were changed. The reason was simple. What Goldstein assumed to be a proton was actually an ion. He gave up his work there, but promised that "he would return." However, he was widely ignored.


Protons are spin −1/2 fermions and are composed of three quarks, making them baryons. The two up quarks and one down quark of the proton are held together by the strong force, mediated by gluons.
Protons and neutrons are both nucleons, which may be bound by the nuclear force into atomic nuclei. The nucleus of the most common isotope of the hydrogen atom is a single proton (it contains no neutrons). The nuclei of heavy hydrogen (deuterium and tritium) contain neutrons. All other types atoms are composed of two or more protons and various numbers of neutrons. The number of protons in the nucleus determines the chemical properties of the atom and thus which chemical element is represented; it is the number of both neutrons and protons in a nuclide which determine the particular isotope of an element.


The antiparticle of the proton is the antiproton. It was discovered in 1955 by Emilio Segrè and Owen Chamberlain, for which they were awarded the 1959 Nobel Prize in Physics.
CPT-symmetry puts strong constraints on the relative properties of particles and antiparticles and, therefore, is open to stringent tests. For example, the charges of the proton and antiproton must sum to exactly zero. This equality has been tested to one part in 10. The equality of their masses is also tested to better than one part in 10. By holding antiprotons in a Penning trap, the equality of the charge to mass ratio of the proton and the antiproton has been tested to 1 part in . The magnetic moment of the antiproton has been measured with error of nuclear Bohr magnetons, and is found to be equal and opposite to that of the proton.

High-energy physics

Due to their stability and large mass (relative to electrons), protons are well suited to use in particle colliders such as the Large Hadron Collider at CERN and the Tevatron at Fermilab. Protons also make up a large majority of the cosmic rays which impinge on the Earth's atmosphere. Such high-energy proton collisions are more complicated to study than electron collisions, due to the composite nature of the proton. Understanding the details of proton structure requires quantum chromodynamics.

See also


proton in Afrikaans: Proton
proton in Arabic: بروتون
proton in Asturian: Protón
proton in Bengali: প্রোটন
proton in Min Nan: Iông-chú
proton in Banyumasan: Proton
proton in Belarusian (Tarashkevitsa): Пратон
proton in Bosnian: Proton
proton in Breton: Proton
proton in Bulgarian: Протон
proton in Catalan: Protó
proton in Chuvash: Протон
proton in Czech: Proton
proton in Welsh: Proton
proton in Danish: Proton
proton in German: Proton
proton in Estonian: Prooton
proton in Modern Greek (1453-): Πρωτόνιο
proton in Spanish: Protón
proton in Esperanto: Protono
proton in Basque: Protoi
proton in Persian: پروتون
proton in French: Proton
proton in Irish: Prótón
proton in Galician: Protón
proton in Classical Chinese: 質子
proton in Korean: 양성자
proton in Hindi: प्रोटॉन
proton in Croatian: Proton
proton in Ido: Protono
proton in Indonesian: Proton
proton in Interlingua (International Auxiliary Language Association): Proton
proton in Icelandic: Róteind
proton in Italian: Protone
proton in Hebrew: פרוטון
proton in Kannada: ಪ್ರೋಟಾನ್
proton in Swahili (macrolanguage): Protoni
proton in Latin: Proton
proton in Latvian: Protons
proton in Lithuanian: Protonas
proton in Lingala: Proton
proton in Lombard: Prutún
proton in Hungarian: Proton
proton in Macedonian: Протон
proton in Malayalam: പ്രോട്ടോണ്‍
proton in Malay (macrolanguage): Proton
proton in Mongolian: Протон
proton in Dutch: Proton (deeltje)
proton in Japanese: 陽子
proton in Norwegian: Proton
proton in Norwegian Nynorsk: Proton
proton in Novial: Protone
proton in Occitan (post 1500): Proton
proton in Low German: Proton
proton in Polish: Proton
proton in Portuguese: Próton
proton in Kölsch: Proton
proton in Romanian: Proton
proton in Quechua: Prutun
proton in Russian: Протон
proton in Albanian: Protoni
proton in Sicilian: Prutoni
proton in Simple English: Proton
proton in Slovak: Protón
proton in Slovenian: Proton
proton in Serbian: Протон
proton in Serbo-Croatian: Proton
proton in Saterfriesisch: Proton
proton in Sundanese: Proton
proton in Finnish: Protoni
proton in Swedish: Proton
proton in Tamil: நேர்மின்னி
proton in Thai: โปรตอน
proton in Vietnamese: Proton
proton in Turkish: Proton
proton in Ukrainian: Протон
proton in Urdu: اولیہ (جوہر)
proton in Venetian: Proton
proton in Yoruba: Àkọ́wá
proton in Samogitian: Pruotuons
proton in Chinese: 質子

Synonyms, Antonyms and Related Words

Kern, NMR, alpha particle, antibaryon, antilepton, antimeson, atom, atomic nucleus, atomic particle, baryon, beta particle, electron, elementary particle, ion, lepton, meson, molecule, monad, neutron, nuclear force, nuclear magnetic resonance, nuclear particle, nuclear resonance, nucleon, nucleosynthesis, nucleus, photon, quark, strangeness, strong interaction, triton, valence electron
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