Editing Subatomic particle (section)

{{Short description|Particle smaller than an atom}}
[[File:Quark structure proton.svg|thumb|upright=0.8|A composite particle [[proton]] is made of two [[up quark]]s and one [[down quark]], which are [[elementary particle]]s.]]

In [[physics]], a '''subatomic particle''' is a [[particle]] smaller than an [[atom]].<ref>{{cite web|title=Subatomic particles|url=http://www.ndt-ed.org/EducationResources/HighSchool/Radiography/subatomicparticles.htm|publisher=NTD|access-date=5 June 2012|archive-date=16 February 2014|archive-url=https://web.archive.org/web/20140216092512/http://www.ndt-ed.org/EducationResources/HighSchool/Radiography/subatomicparticles.htm|url-status=dead}}</ref> According to the [[Standard Model|Standard Model of particle physics]], a subatomic particle can be either a [[composite particle]], which is composed of other particles (for example, a [[baryon]], like a [[proton]] or a [[neutron]], composed of three [[quarks]]; or a [[meson]], composed of two [[Quark|quarks]]), or an [[elementary particle]], which is not composed of other particles (for example, quarks; or [[electrons]], [[muons]], and [[Tau (particle)|tau]] particles, which are called [[leptons]]).<ref>{{cite book|last=Bolonkin|first=Alexander|title=Universe, Human Immortality and Future Human Evaluation|date=2011|publisher=[[Elsevier]]|isbn=9780124158016|pages=25}}</ref> [[Particle physics]] and [[nuclear physics]] study these particles and how they interact.<ref>
{{cite book
 | last = Fritzsch  | first = Harald
 | date = 2005
 | title = Elementary Particles
 | url = https://archive.org/details/elementarypartic0000frit
 | url-access = registration  | pages = [https://archive.org/details/elementarypartic0000frit/page/11 11]–20
 | publisher = [[World Scientific]]
 | isbn = 978-981-256-141-1
}}</ref> Most force-carrying particles like [[photons]] or [[gluons]] are called [[bosons]] and, although they have quanta of energy, do not have rest mass or discrete diameters (other than pure energy wavelength) and are unlike the former particles that have rest mass and cannot overlap or combine which are called [[fermions]]. The [[W and Z bosons]], however, are an exception to this rule and have relatively large rest masses at approximately {{val|80|ul=GeV/c2}} and {{val|90|u=GeV/c2}} respectively.

Experiments show that light could behave like a [[stream of particles]] (called [[photon]]s) as well as exhibiting wave-like properties. This led to the concept of [[wave–particle duality]] to reflect that quantum-scale {{em|particles}} behave both like particles and like [[wave]]s; they are occasionally called ''wavicles'' to reflect this.<ref>{{cite book|url=https://doi.org/10.1007/978-1-4684-5386-7_18|title=Quantum Uncertainties: Recent and Future Experiments and Interpretations|first1=Geoffrey|last1=Hunter|first2=Robert L. P.|last2=Wadlinger|editor-first1=William M.|editor-last1=Honig|editor-first2=David W.|editor-last2=Kraft|editor-first3=Emilio|editor-last3=Panarella|date=August 23, 1987|publisher=Springer US|pages=331–343|via=Springer Link|doi=10.1007/978-1-4684-5386-7_18 |quote=The finite-field model of the photon is both a particle and a wave, and hence we refer to it by Eddington's name "wavicle". }}</ref>

Another concept, the [[uncertainty principle]], states that some of their properties taken together, such as their simultaneous [[position (vector)|position]] and [[momentum]], cannot be measured exactly.<ref>{{cite journal |last=Heisenberg |first=W. |date=1927 |title=Über den anschaulichen Inhalt der quantentheoretischen Kinematik und Mechanik |journal=[[Zeitschrift für Physik]] |language=de |volume=43 |issue=3–4 |pages=172–198 |bibcode=1927ZPhy...43..172H |doi=10.1007/BF01397280 |s2cid=122763326 }}</ref> 
Interactions of particles in the framework of [[quantum field theory]] are understood as creation and annihilation of ''[[quantum|quanta]]'' of corresponding [[fundamental interaction]]s. This blends particle physics with [[Quantum field theory|field theory]].

Even among [[particle physics|particle physicists]], the exact definition of a particle has diverse descriptions. These professional attempts at the definition of a particle include:<ref>{{cite web |date=12 November 2020 |title=What is a Particle? |url=https://www.quantamagazine.org/what-is-a-particle-20201112/}}</ref>  
* A particle is a [[wave function collapse|collapsed wave function]]
* A particle is an excitation of a [[Quantum field theory|quantum field]]
* A particle is an [[Poincaré group|irreducible representation of the Poincaré group]]
* A particle is an observed thing

{| class="wikitable"
|+ Particles in the atom
! Subatomic particle !! Symbol !! Type !! Location in atom !! Charge{{br}}{{bracket|''[[Elementary charge|e]]''}} !! Mass{{br}}{{bracket|[[Dalton (unit)|Da]]}}
|-
| proton || p<sup>+</sup> || composite || nucleus || +1 || ≈ 1
|-
| neutron || n<sup>0</sup> || composite || nucleus || 0 || ≈ 1
|-
| electron || e<sup>−</sup> || elementary || shells || −1 || ≈ {{sfrac|1|2000}}
|}