Menu
Home
People
Places
Arts
History
Plants & Animals
Science
Life & Culture
Technology
Reference.org
Subatomic particle
open-in-new
<p>In <a href="/facts/Physics/a7aH2y08">physics</a>, a subatomic particle is a <a href="/facts/Particle/JHKr2w6h">particle</a> smaller than an <a href="/facts/Atom/FoQ4kGN5">atom</a>. According to the <a href="/facts/Standard_Model/LhVGf9ow">Standard Model of particle physics</a>, a subatomic particle can be either a <a href="/facts/Composite_particle/FwR0Ab6u">composite particle</a>, which is composed of other particles (for example, a <a href="/facts/Baryon/QFwAUWK2">baryon</a>, like a <a href="/facts/Proton/clCjepXP">proton</a> or a <a href="/facts/Neutron/oRCM1geb">neutron</a>, composed of three <a href="/facts/Quarks/hwuuVkV5">quarks</a>; or a <a href="/facts/Meson/9R0kIc1q">meson</a>, composed of two <a href="/facts/Quark/hwuuVkV5">quarks</a>), or an <a href="/facts/Elementary_particle/CTFDM97U">elementary particle</a>, which is not composed of other particles (for example, quarks; or <a href="/facts/Electrons/L0KBo5cW">electrons</a>, <a href="/facts/Muons/BP2fLVIR">muons</a>, and <a href="/facts/Tau_(particle)/6DW8j6PC">tau</a> particles, which are called <a href="/facts/Leptons/X4a6MGop">leptons</a>). <a href="/facts/Particle_physics/YgIuyj2t">Particle physics</a> and <a href="/facts/Nuclear_physics/fzQbt1aF">nuclear physics</a> study these particles and how they interact. Most force-carrying particles like <a href="/facts/Photons/mFNhAEzA">photons</a> or <a href="/facts/Gluons/t6YH8I21">gluons</a> are called <a href="/facts/Bosons/XtPFcjb5">bosons</a> 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 <a href="/facts/Fermions/LEckdDsR">fermions</a>. The <a href="/facts/W_and_Z_bosons/gAncY5XV">W and Z bosons</a>, however, are an exception to this rule and have relatively large rest masses at approximately 80 <a href="/facts/Electronvolt/YMT1fqX9">GeV</a> and 90 GeV respectively. </p><p>Experiments show that light could behave like a <a href="/facts/Stream_of_particles/mg5EIlWb">stream of particles</a> (called <a href="/facts/Photon/mFNhAEzA">photons</a>) as well as exhibiting wave-like properties. This led to the concept of <a href="/facts/Wave%E2%80%93particle_duality/Au3UlcwQ">wave–particle duality</a> to reflect that quantum-scale particles behave both like particles and like <a href="/facts/Wave/fU0HH6St">waves</a>; they are occasionally called wavicles to reflect this. </p><p>Another concept, the <a href="/facts/Uncertainty_principle/UUSoSp4T">uncertainty principle</a>, states that some of their properties taken together, such as their simultaneous <a href="/facts/Position_(vector)/Tpk5d9f2">position</a> and <a href="/facts/Momentum/TTkGv5eY">momentum</a>, cannot be measured exactly. Interactions of particles in the framework of <a href="/facts/Quantum_field_theory/VoewsNJV">quantum field theory</a> are understood as creation and annihilation of <i><a href="/facts/Quantum/4x5QTxGB">quanta</a></i> of corresponding <a href="/facts/Fundamental_interaction/WrFEJaFl">fundamental interactions</a>. This blends particle physics with <a href="/facts/Quantum_field_theory/VoewsNJV">field theory</a>. </p><p>Even among <a href="/facts/Particle_physics/YgIuyj2t">particle physicists</a>, the exact definition of a particle has diverse descriptions. These professional attempts at the definition of a particle include: </p> <ul><li>A particle is a <a href="/facts/Wave_function_collapse/f7KvbBHK">collapsed wave function</a></li> <li>A particle is a <a href="/facts/Quantum_excitation_(accelerator_physics)/VUeK80rA">quantum excitation of a field</a></li> <li>A particle is an <a href="/facts/Poincar%C3%A9_group/3IerRYG1">irreducible representation of the Poincaré group</a></li> <li>A particle is an observed thing</li></ul> Particles in the atom<table><tbody><tr><th>Subatomic particle</th><th>Symbol</th><th>Type</th><th>Location in atom</th><th>Charge(<i><a href="/facts/Elementary_charge/lPcj6CoQ">e</a></i>)</th><th>Mass(<a href="/facts/Dalton_(unit)/IMATU3vf">Da</a>)</th></tr><tr><td>Proton</td><td>p+</td><td>Composite</td><td>Nucleus</td><td>+1</td><td>≈ 1</td></tr><tr><td>Neutron</td><td>n0</td><td>Composite</td><td>Nucleus</td><td>0</td><td>≈ 1</td></tr><tr><td>Electron</td><td>e−</td><td>Elementary</td><td>Shells</td><td>−1</td><td>≈ 1/2000</td></tr></tbody></table>