physics Physics is the scientific study of matter, its Elementary particle, fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge whi ...

, a subatomic particle is a

particle In the physical sciences, a particle (or corpuscle in older texts) is a small localized object which can be described by several physical or chemical properties, such as volume, density, or mass. They vary greatly in size or quantity, from s ...

smaller than an

atom Atoms are the basic particles of the chemical elements. An atom consists of a atomic nucleus, nucleus of protons and generally neutrons, surrounded by an electromagnetically bound swarm of electrons. The chemical elements are distinguished fr ...

. According to the Standard Model of particle physics, a subatomic particle can be either a

composite particle This is a list of known and hypothesized microscopic particles in particle physics, condensed matter physics and cosmology. Standard Model elementary particles Elementary particles are particles with no measurable internal structure; that is, ...

, which is composed of other particles (for example, a

baryon In particle physics, a baryon is a type of composite particle, composite subatomic particle that contains an odd number of valence quarks, conventionally three. proton, Protons and neutron, neutrons are examples of baryons; because baryons are ...

, like a

proton A proton is a stable subatomic particle, symbol , Hydron (chemistry), H+, or 1H+ with a positive electric charge of +1 ''e'' (elementary charge). Its mass is slightly less than the mass of a neutron and approximately times the mass of an e ...

or a

neutron The neutron is a subatomic particle, symbol or , that has no electric charge, and a mass slightly greater than that of a proton. The Discovery of the neutron, neutron was discovered by James Chadwick in 1932, leading to the discovery of nucle ...

, composed of three

quarks A quark () is a type of elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. All commonly o ...

; or a

meson In particle physics, a meson () is a type of hadronic subatomic particle composed of an equal number of quarks and antiquarks, usually one of each, bound together by the strong interaction. Because mesons are composed of quark subparticles, the ...

, composed of two

), or an

elementary particle In particle physics, an elementary particle or fundamental particle is a subatomic particle that is not composed of other particles. The Standard Model presently recognizes seventeen distinct particles—twelve fermions and five bosons. As a c ...

, which is not composed of other particles (for example, quarks; or

electrons The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary charge, elementary electric charge. It is a fundamental particle that comprises the ordinary matter that makes up the universe, along with up qua ...

, muons, and

tau Tau (; uppercase Τ, lowercase τ or \boldsymbol\tau; ) is the nineteenth letter of the Greek alphabet, representing the voiceless alveolar plosive, voiceless dental or alveolar plosive . In the system of Greek numerals, it has a value of 300 ...

particles, which are called leptons).

Particle physics Particle physics or high-energy physics is the study of Elementary particle, fundamental particles and fundamental interaction, forces that constitute matter and radiation. The field also studies combinations of elementary particles up to the s ...

and

nuclear physics Nuclear physics is the field of physics that studies atomic nuclei and their constituents and interactions, in addition to the study of other forms of nuclear matter. Nuclear physics should not be confused with atomic physics, which studies th ...

study these particles and how they interact. Most force-carrying particles like

photons A photon () is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are massless particles that ...

gluons A gluon ( ) is a type of massless elementary particle that mediates the strong interaction between quarks, acting as the exchange particle for the interaction. Gluons are massless vector bosons, thereby having a spin of 1. Through the s ...

are called

bosons In particle physics, a boson ( ) is a subatomic particle whose spin quantum number has an integer value (0, 1, 2, ...). Bosons form one of the two fundamental classes of subatomic particle, the other being fermions, which have half odd-integer ...

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 In particle physics, the W and Z bosons are vector bosons that are together known as the weak bosons or more generally as the intermediate vector bosons. These elementary particles mediate the weak interaction; the respective symbols are , , an ...

, however, are an exception to this rule and have relatively large rest masses at approximately and respectively. Experiments show that light could behave like a

stream of particles A stream is a continuous body of water, body of surface water Current (stream), flowing within the stream bed, bed and bank (geography), banks of a channel (geography), channel. Depending on its location or certain characteristics, a strea ...

(called

photon A photon () is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are massless particles that can ...

s) as well as exhibiting wave-like properties. This led to the concept of

wave–particle duality Wave–particle duality is the concept in quantum mechanics that fundamental entities of the universe, like photons and electrons, exhibit particle or wave (physics), wave properties according to the experimental circumstances. It expresses the in ...

to reflect that quantum-scale behave both like particles and like

wave In physics, mathematics, engineering, and related fields, a wave is a propagating dynamic disturbance (change from List of types of equilibrium, equilibrium) of one or more quantities. ''Periodic waves'' oscillate repeatedly about an equilibrium ...

s; they are occasionally called ''wavicles'' to reflect this. Another concept, the

uncertainty principle The uncertainty principle, also known as Heisenberg's indeterminacy principle, is a fundamental concept in quantum mechanics. It states that there is a limit to the precision with which certain pairs of physical properties, such as position a ...

, states that some of their properties taken together, such as their simultaneous position and

momentum In Newtonian mechanics, momentum (: momenta or momentums; more specifically linear momentum or translational momentum) is the product of the mass and velocity of an object. It is a vector quantity, possessing a magnitude and a direction. ...

, cannot be measured exactly. Interactions of particles in the framework of

quantum field theory In theoretical physics, quantum field theory (QFT) is a theoretical framework that combines Field theory (physics), field theory and the principle of relativity with ideas behind quantum mechanics. QFT is used in particle physics to construct phy ...

are understood as creation and annihilation of '' quanta'' of corresponding

fundamental interaction In physics, the fundamental interactions or fundamental forces are interactions in nature that appear not to be reducible to more basic interactions. There are four fundamental interactions known to exist: * gravity * electromagnetism * weak int ...

s. This blends particle physics with field theory. Even among

particle physicists Particle physics or high-energy physics is the study of fundamental particles and forces that constitute matter and radiation. The field also studies combinations of elementary particles up to the scale of protons and neutrons, while the stud ...

, the exact definition of a particle has diverse descriptions. These professional attempts at the definition of a particle include: * A particle is a collapsed wave function * A particle is an excitation of a quantum field * A particle is an irreducible representation of the Poincaré group * A particle is an observed thing

Classification

By composition

Subatomic particles are either "elementary", i.e. not made of multiple other particles, or "composite" and made of more than one elementary particle bound together. The elementary particles of the

Standard Model The Standard Model of particle physics is the Scientific theory, theory describing three of the four known fundamental forces (electromagnetism, electromagnetic, weak interaction, weak and strong interactions – excluding gravity) in the unive ...

are: * Six "

flavors Flavour or flavor is either the sensory perception of taste or smell, or a flavoring in food that produces such perception. Flavour or flavor may also refer to: Science * Flavors (programming language), an early object-oriented extension to L ...

" of

quark A quark () is a type of elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nucleus, atomic nuclei ...

s: up, down,

strange Strange may refer to: Fiction * Strange (comic book), a comic book limited series by Marvel Comics * Strange (Marvel Comics), one of a pair of Marvel Comics characters known as The Strangers * Adam Strange, a DC Comics superhero * The title c ...

, charm, bottom, and

top Top most commonly refers to: * Top, a basic term of orientation, distinguished from bottom, front, back, and sides * Spinning top, a ubiquitous traditional toy * Top (clothing), clothing designed to be worn over the torso * Mountain top, a moun ...

; * Six types of

lepton In particle physics, a lepton is an elementary particle of half-integer spin (Spin (physics), spin ) that does not undergo strong interactions. Two main classes of leptons exist: electric charge, charged leptons (also known as the electron-li ...

electron The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary charge, elementary electric charge. It is a fundamental particle that comprises the ordinary matter that makes up the universe, along with up qua ...

electron neutrino The electron neutrino () is an elementary particle which has zero electric charge and a spin of . Together with the electron, it forms the first generation of leptons, hence the name ''electron neutrino''. It was first hypothesized by Wolfga ...

muon A muon ( ; from the Greek letter mu (μ) used to represent it) is an elementary particle similar to the electron, with an electric charge of −1 '' e'' and a spin of ''ħ'', but with a much greater mass. It is classified as a ...

muon neutrino The muon neutrino is an elementary particle which has the symbol and zero electric charge. Together with the muon it forms the second generation of leptons, hence the name muon neutrino. It was discovered in 1962 by Leon Lederman, Melvin Schwa ...

, tau neutrino; * Twelve

gauge boson In particle physics, a gauge boson is a bosonic elementary particle that acts as the force carrier for elementary fermions. Elementary particles whose interactions are described by a gauge theory interact with each other by the exchange of gauge ...

s (force carriers): the photon of

electromagnetism In physics, electromagnetism is an interaction that occurs between particles with electric charge via electromagnetic fields. The electromagnetic force is one of the four fundamental forces of nature. It is the dominant force in the interacti ...

, the three W and Z bosons of the weak force, and the eight gluons of the

strong force In nuclear physics and particle physics, the strong interaction, also called the strong force or strong nuclear force, is one of the four known fundamental interactions. It confines quarks into protons, neutrons, and other hadron particles, an ...

; * The

Higgs boson The Higgs boson, sometimes called the Higgs particle, is an elementary particle in the Standard Model of particle physics produced by the excited state, quantum excitation of the Higgs field, one of the field (physics), fields in particl ...

All of these have now been discovered through experiments, with the latest being the top quark (1995), tau neutrino (2000), and Higgs boson (2012). Various extensions of the Standard Model predict the existence of an elementary

graviton In theories of quantum gravity, the graviton is the hypothetical elementary particle that mediates the force of gravitational interaction. There is no complete quantum field theory of gravitons due to an outstanding mathematical problem with re ...

particle and many other elementary particles, but none have been discovered as of 2021.

Hadrons

The word hadron comes from Greek and was introduced in 1962 by Lev Okun. Nearly all composite particles contain multiple quarks (and/or antiquarks) bound together by gluons (with a few exceptions with no quarks, such as

positronium Positronium (Ps) is a system consisting of an electron and its antimatter, anti-particle, a positron, bound together into an exotic atom, specifically an onium. Unlike hydrogen, the system has no protons. The system is unstable: the two part ...

and muonium). Those containing few (≤ 5) quarks (including antiquarks) are called

hadron In particle physics, a hadron is a composite subatomic particle made of two or more quarks held together by the strong nuclear force. Pronounced , the name is derived . They are analogous to molecules, which are held together by the electri ...

s. Due to a property known as

color confinement In quantum chromodynamics (QCD), color confinement, often simply called confinement, is the phenomenon that color-charged particles (such as quarks and gluons) cannot be isolated, and therefore cannot be directly observed in normal conditions b ...

, quarks are never found singly but always occur in hadrons containing multiple quarks. The hadrons are divided by number of quarks (including antiquarks) into the baryons containing an odd number of quarks (almost always 3), of which the

and

(the two

nucleons In physics and chemistry, a nucleon is either a proton or a neutron, considered in its role as a component of an atomic nucleus. The number of nucleons in a nucleus defines the atom's mass number. Until the 1960s, nucleons were thought to be ele ...

) are by far the best known; and the

s containing an even number of quarks (almost always 2, one quark and one antiquark), of which the

pion In particle physics, a pion (, ) or pi meson, denoted with the Greek alphabet, Greek letter pi (letter), pi (), is any of three subatomic particles: , , and . Each pion consists of a quark and an antiquark and is therefore a meson. Pions are the ...

s and

kaon In particle physics, a kaon, also called a K meson and denoted , is any of a group of four mesons distinguished by a quantum number called strangeness. In the quark model they are understood to be bound states of a strange quark (or antiquark ...

s are the best known. Except for the proton and neutron, all other hadrons are unstable and decay into other particles in microseconds or less. A proton is made of two

up quark The up quark or u quark (symbol: u) is the lightest of all quarks, a type of elementary particle, and a significant constituent of matter. It, along with the down quark, forms the neutrons (one up quark, two down quarks) and protons (two up quark ...

s and one

down quark The down quark (symbol: d) is a type of elementary particle, and a major constituent of matter. The down quark is the second-lightest of all quarks, and combines with other quarks to form composite particles called hadrons. Down quarks are most ...

, while the neutron is made of two down quarks and one up quark. These commonly bind together into an atomic nucleus, e.g. a helium-4 nucleus is composed of two protons and two neutrons. Most hadrons do not live long enough to bind into nucleus-like composites; those that do (other than the proton and neutron) form exotic nuclei.

By statistics

Any subatomic particle, like any particle in the

three-dimensional space In geometry, a three-dimensional space (3D space, 3-space or, rarely, tri-dimensional space) is a mathematical space in which three values ('' coordinates'') are required to determine the position of a point. Most commonly, it is the three- ...

that obeys the

laws Law is a set of rules that are created and are law enforcement, enforceable by social or governmental institutions to regulate behavior, with its precise definition a matter of longstanding debate. It has been variously described as a Socia ...

quantum mechanics Quantum mechanics is the fundamental physical Scientific theory, theory that describes the behavior of matter and of light; its unusual characteristics typically occur at and below the scale of atoms. Reprinted, Addison-Wesley, 1989, It is ...

, can be either a boson (with integer spin) or a fermion (with odd half-integer spin). In the Standard Model, all the elementary fermions have spin 1/2, and are divided into the quarks which carry color charge and therefore feel the strong interaction, and the leptons which do not. The elementary bosons comprise the gauge bosons (photon, W and Z, gluons) with spin 1, while the Higgs boson is the only elementary particle with spin zero. The hypothetical graviton is required theoretically to have spin 2, but is not part of the Standard Model. Some extensions such as

supersymmetry Supersymmetry is a Theory, theoretical framework in physics that suggests the existence of a symmetry between Particle physics, particles with integer Spin (physics), spin (''bosons'') and particles with half-integer spin (''fermions''). It propo ...

predict additional elementary particles with spin 3/2, but none have been discovered as of 2023. Due to the laws for spin of composite particles, the baryons (3 quarks) have spin either 1/2 or 3/2 and are therefore fermions; the mesons (2 quarks) have integer spin of either 0 or 1 and are therefore bosons.

By mass

special relativity In physics, the special theory of relativity, or special relativity for short, is a scientific theory of the relationship between Spacetime, space and time. In Albert Einstein's 1905 paper, Annus Mirabilis papers#Special relativity, "On the Ele ...

, the energy of a particle at rest equals its mass times the speed of light squared, ''E'' = ''mc''². That is,

mass Mass is an Intrinsic and extrinsic properties, intrinsic property of a physical body, body. It was traditionally believed to be related to the physical quantity, quantity of matter in a body, until the discovery of the atom and particle physi ...

can be expressed in terms of

energy Energy () is the physical quantity, quantitative physical property, property that is transferred to a physical body, body or to a physical system, recognizable in the performance of Work (thermodynamics), work and in the form of heat and l ...

and vice versa. If a particle has a

frame of reference In physics and astronomy, a frame of reference (or reference frame) is an abstract coordinate system, whose origin (mathematics), origin, orientation (geometry), orientation, and scale (geometry), scale have been specified in physical space. It ...

in which it lies at rest, then it has a positive

rest mass The invariant mass, rest mass, intrinsic mass, proper mass, or in the case of bound systems simply mass, is the portion of the total mass of an object or system of objects that is independent of the overall motion of the system. More precisely, ...

and is referred to as ''massive''. All composite particles are massive. Baryons (meaning "heavy") tend to have greater mass than mesons (meaning "intermediate"), which in turn tend to be heavier than leptons (meaning "lightweight"), but the heaviest lepton (the tau particle) is heavier than the two lightest flavours of baryons (

nucleon In physics and chemistry, a nucleon is either a proton or a neutron, considered in its role as a component of an atomic nucleus. The number of nucleons in a nucleus defines the atom's mass number. Until the 1960s, nucleons were thought to be ele ...

s). It is also certain that any particle with an

electric charge Electric charge (symbol ''q'', sometimes ''Q'') is a physical property of matter that causes it to experience a force when placed in an electromagnetic field. Electric charge can be ''positive'' or ''negative''. Like charges repel each other and ...

is massive. When originally defined in the 1950s, the terms baryons, mesons and leptons referred to masses; however, after the quark model became accepted in the 1970s, it was recognised that baryons are composites of three quarks, mesons are composites of one quark and one antiquark, while leptons are elementary and are defined as the elementary fermions with no color charge. All

massless particle In particle physics, a massless particle is an elementary particle whose invariant mass is zero. At present the only confirmed massless particle is the photon. Other particles and quasiparticles Standard Model gauge bosons The photon (carrier of ...

s (particles whose

invariant mass The invariant mass, rest mass, intrinsic mass, proper mass, or in the case of bound systems simply mass, is the portion of the total mass of an object or system of objects that is independent of the overall motion of the system. More precisely, ...

is zero) are elementary. These include the photon and gluon, although the latter cannot be isolated.

By decay

Most subatomic particles are not stable. All leptons, as well as baryons decay by either the strong force or weak force (except for the proton). Protons are not known to decay, although whether they are "truly" stable is unknown, as some very important Grand Unified Theories (GUTs) actually require it. The μ and τ muons, as well as their antiparticles, decay by the weak force. Neutrinos (and antineutrinos) do not decay, but a related phenomenon of

neutrino oscillation Neutrino oscillation is a quantum mechanics, quantum mechanical phenomenon in which a neutrino created with a specific lepton lepton number, family number ("lepton flavor": electron, muon, or tau lepton, tau) can later be Quantum measurement, mea ...

s is thought to exist even in vacuums. The electron and its antiparticle, the

positron The positron or antielectron is the particle with an electric charge of +1''elementary charge, e'', a Spin (physics), spin of 1/2 (the same as the electron), and the same Electron rest mass, mass as an electron. It is the antiparticle (antimatt ...

, are theoretically stable due to

charge conservation In physics, charge conservation is the principle, of experimental nature, that the total electric charge in an isolated system never changes. The net quantity of electric charge, the amount of positive charge minus the amount of negative charg ...

unless a lighter particle having

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

of electric charge ''e'' exists (which is unlikely). Its charge is not shown yet.

Other properties

All observable subatomic particles have their electric charge an

integer An integer is the number zero (0), a positive natural number (1, 2, 3, ...), or the negation of a positive natural number (−1, −2, −3, ...). The negations or additive inverses of the positive natural numbers are referred to as negative in ...

multiple of the

elementary charge The elementary charge, usually denoted by , is a fundamental physical constant, defined as the electric charge carried by a single proton (+1 ''e'') or, equivalently, the magnitude of the negative electric charge carried by a single electron, ...

. The Standard Model's quarks have "non-integer" electric charges, namely, multiple of ''e'', but quarks (and other combinations with non-integer electric charge) cannot be isolated due to

. For baryons, mesons, and their antiparticles the constituent quarks' charges sum up to an integer multiple of ''e''. Through the work of

Albert Einstein Albert Einstein (14 March 187918 April 1955) was a German-born theoretical physicist who is best known for developing the theory of relativity. Einstein also made important contributions to quantum mechanics. His mass–energy equivalence f ...

Satyendra Nath Bose Satyendra Nath Bose (; 1 January 1894 – 4 February 1974) was an Indian theoretical physicist and mathematician. He is best known for his work on quantum mechanics in the early 1920s, in developing the foundation for Bose–Einstein statist ...

, Louis de Broglie, and many others, current scientific theory holds that ''all'' particles also have a wave nature. This has been verified not only for elementary particles but also for compound particles like atoms and even molecules. In fact, according to traditional formulations of non-relativistic quantum mechanics, wave–particle duality applies to all objects, even macroscopic ones; although the wave properties of macroscopic objects cannot be detected due to their small wavelengths. Interactions between particles have been scrutinized for many centuries, and a few simple laws underpin how particles behave in collisions and interactions. The most fundamental of these are the laws of

conservation of energy The law of conservation of energy states that the total energy of an isolated system remains constant; it is said to be Conservation law, ''conserved'' over time. In the case of a Closed system#In thermodynamics, closed system, the principle s ...

and

conservation of momentum In Newtonian mechanics, momentum (: momenta or momentums; more specifically linear momentum or translational momentum) is the product of the mass and velocity of an object. It is a vector quantity, possessing a magnitude and a direction. ...

, which let us make calculations of particle interactions on scales of magnitude that range from stars to quarks. These are the prerequisite basics of

Newtonian mechanics Newton's laws of motion are three physical laws that describe the relationship between the motion of an object and the forces acting on it. These laws, which provide the basis for Newtonian mechanics, can be paraphrased as follows: # A body r ...

, a series of statements and equations in ''

Philosophiae Naturalis Principia Mathematica Philosophy ('love of wisdom' in Ancient Greek) is a systematic study of general and fundamental questions concerning topics like existence, reason, knowledge, value, mind, and language. It is a rational and critical inquiry that reflects on ...

'', originally published in 1687.

Dividing an atom

The negatively charged electron has a mass of about of that of a

hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

atom. The remainder of the hydrogen atom's mass comes from the positively charged

. The

atomic number The atomic number or nuclear charge number (symbol ''Z'') of a chemical element is the charge number of its atomic nucleus. For ordinary nuclei composed of protons and neutrons, this is equal to the proton number (''n''p) or the number of pro ...

of an element is the number of protons in its nucleus. Neutrons are neutral particles having a mass slightly greater than that of the proton. Different

isotope Isotopes are distinct nuclear species (or ''nuclides'') of the same chemical element. They have the same atomic number (number of protons in their Atomic nucleus, nuclei) and position in the periodic table (and hence belong to the same chemica ...

s of the same element contain the same number of protons but different numbers of neutrons. The

mass number The mass number (symbol ''A'', from the German word: ''Atomgewicht'', "atomic weight"), also called atomic mass number or nucleon number, is the total number of protons and neutrons (together known as nucleons) in an atomic nucleus. It is appro ...

of an isotope is the total number of

s (neutrons and protons collectively).

Chemistry Chemistry is the scientific study of the properties and behavior of matter. It is a physical science within the natural sciences that studies the chemical elements that make up matter and chemical compound, compounds made of atoms, molecules a ...

concerns itself with how electron sharing binds atoms into structures such as crystals and

molecule A molecule is a group of two or more atoms that are held together by Force, attractive forces known as chemical bonds; depending on context, the term may or may not include ions that satisfy this criterion. In quantum physics, organic chemi ...

s. The subatomic particles considered important in the understanding of chemistry are the

, the

, and the

Nuclear physics Nuclear physics is the field of physics that studies atomic nuclei and their constituents and interactions, in addition to the study of other forms of nuclear matter. Nuclear physics should not be confused with atomic physics, which studies th ...

deals with how protons and neutrons arrange themselves in nuclei. The study of subatomic particles, atoms and molecules, and their structure and interactions, requires

. Analyzing processes that change the numbers and types of particles requires

. The study of subatomic particles ''per se'' is called

particle physics Particle physics or high-energy physics is the study of Elementary particle, fundamental particles and fundamental interaction, forces that constitute matter and radiation. The field also studies combinations of elementary particles up to the s ...

. The term ''

high-energy physics Particle physics or high-energy physics is the study of fundamental particles and forces that constitute matter and radiation. The field also studies combinations of elementary particles up to the scale of protons and neutrons, while the stu ...

'' is nearly synonymous to "particle physics" since creation of particles requires high energies: it occurs only as a result of

cosmic ray Cosmic rays or astroparticles are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the ...

s, or in

particle accelerator A particle accelerator is a machine that uses electromagnetic fields to propel electric charge, charged particles to very high speeds and energies to contain them in well-defined particle beam, beams. Small accelerators are used for fundamental ...

s. Particle phenomenology systematizes the knowledge about subatomic particles obtained from these experiments.

History

The term "''subatomic'' particle" is largely a

retronym A retronym is a newer name for something that differentiates it from something else that is newer, similar, or seen in everyday life; thus, avoiding confusion between the two. Etymology The term ''retronym'', a neologism composed of the combi ...

of the 1960s, used to distinguish a large number of

s and

s (which comprise

s) from particles that are now thought to be truly elementary. Before that hadrons were usually classified as "elementary" because their composition was unknown. A list of important discoveries follows: {, class="wikitable" !Particle !Composition !Theorized !Discovered !Comments , - ,

, elementary (

) , G. Johnstone Stoney (1874) , J. J. Thomson (1897) , Minimum unit of electrical charge, for which Stoney suggested the name in 1891. First subatomic particle to be identified. , - ,

alpha particle Alpha particles, also called alpha rays or alpha radiation, consist of two protons and two neutrons bound together into a particle identical to a helium-4 nucleus. They are generally produced in the process of alpha decay but may also be produce ...

, composite (atomic nucleus) , ,

Ernest Rutherford Ernest Rutherford, 1st Baron Rutherford of Nelson (30 August 1871 – 19 October 1937) was a New Zealand physicist who was a pioneering researcher in both Atomic physics, atomic and nuclear physics. He has been described as "the father of nu ...

(1899) , Proven by Rutherford and Thomas Royds in 1907 to be helium nuclei. Rutherford won the Nobel Prize for Chemistry in 1908 for this discovery. , - ,

, elementary (

quantum In physics, a quantum (: quanta) is the minimum amount of any physical entity (physical property) involved in an interaction. The fundamental notion that a property can be "quantized" is referred to as "the hypothesis of quantization". This me ...

) ,

Max Planck Max Karl Ernst Ludwig Planck (; ; 23 April 1858 – 4 October 1947) was a German Theoretical physics, theoretical physicist whose discovery of energy quantum, quanta won him the Nobel Prize in Physics in 1918. Planck made many substantial con ...

(1900) ,

(1905) , Necessary to solve the

thermodynamic Thermodynamics is a branch of physics that deals with heat, work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these quantities is governed by the four laws of th ...

problem of

black-body radiation Black-body radiation is the thermal radiation, thermal electromagnetic radiation within, or surrounding, a body in thermodynamic equilibrium with its environment, emitted by a black body (an idealized opaque, non-reflective body). It has a specific ...

. , - ,

, composite (

) , William Prout (1815) , Ernest Rutherford (1919, named 1920) , The nucleus of . , - ,

, composite (baryon) , Ernest Rutherford (1920) ,

James Chadwick Sir James Chadwick (20 October 1891 – 24 July 1974) was an English nuclear physicist who received the Nobel Prize in Physics in 1935 for his discovery of the neutron. In 1941, he wrote the final draft of the MAUD Report, which inspired t ...

(1932) , The second

. , - ,

antiparticle In particle physics, every type of particle of "ordinary" matter (as opposed to antimatter) is associated with an antiparticle with the same mass but with opposite physical charges (such as electric charge). For example, the antiparticle of the ...

s , ,

Paul Dirac Paul Adrien Maurice Dirac ( ; 8 August 1902 – 20 October 1984) was an English mathematician and Theoretical physics, theoretical physicist who is considered to be one of the founders of quantum mechanics. Dirac laid the foundations for bot ...

(1928) , Carl D. Anderson (, 1932) , Revised explanation uses

CPT symmetry Charge, parity, and time reversal symmetry is a fundamental symmetry of physical laws under the simultaneous transformations of charge conjugation (C), parity transformation (P), and time reversal (T). CPT is the only combination of C, P, and ...

. , - ,

s , composite (

s) ,

Hideki Yukawa Hideki Yukawa (; ; 23 January 1907 – 8 September 1981) was a Japanese theoretical physicist who received the Nobel Prize in Physics in 1949 "for his prediction of the existence of mesons on the basis of theoretical work on nuclear forces". B ...

(1935) , César Lattes, Giuseppe Occhialini, Cecil Powell (1947) , Explains the

nuclear force The nuclear force (or nucleon–nucleon interaction, residual strong force, or, historically, strong nuclear force) is a force that acts between hadrons, most commonly observed between protons and neutrons of atoms. Neutrons and protons, both ...

between nucleons. The first meson (by modern definition) to be discovered. , - ,

, elementary (lepton) , , Carl D. Anderson (1936) , Called a "meson" at first; but today classed as a

. , - ,

, elementary (

) , Antonio Zichichi (1960) , Martin Lewis Perl (1975) , - ,

s {{subatomic particle, kaon , composite (mesons) , {{no, ''never'' , G. D. Rochester, C. C. Butler (1947) , Discovered in

s. The first strange particle. , - , lambda baryons {{subatomic particle, Lambda , composite (baryons) , {{no, ''never'' ,

University of Melbourne The University of Melbourne (colloquially known as Melbourne University) is a public university, public research university located in Melbourne, Australia. Founded in 1853, it is Australia's second oldest university and the oldest in the state ...

({{subatomic particle, Lambda0, 1950) , The first hyperon discovered. , - ,

neutrino A neutrino ( ; denoted by the Greek letter ) is an elementary particle that interacts via the weak interaction and gravity. The neutrino is so named because it is electrically neutral and because its rest mass is so small ('' -ino'') that i ...

{{math, {{subatomic particle, neutrino , elementary (lepton) ,

Wolfgang Pauli Wolfgang Ernst Pauli ( ; ; 25 April 1900 – 15 December 1958) was an Austrian theoretical physicist and a pioneer of quantum mechanics. In 1945, after having been nominated by Albert Einstein, Pauli received the Nobel Prize in Physics "for the ...

(1930), named by

Enrico Fermi Enrico Fermi (; 29 September 1901 – 28 November 1954) was an Italian and naturalized American physicist, renowned for being the creator of the world's first artificial nuclear reactor, the Chicago Pile-1, and a member of the Manhattan Project ...

Clyde Cowan Clyde Lorrain Cowan Jr (December 6, 1919 – May 24, 1974) was an American physicist and the co-discoverer of the neutrino along with Frederick Reines. The discovery was made in 1956 in the neutrino experiment. Reines received the Nobel Prize in ...

Frederick Reines Frederick Reines ( ; March 16, 1918 – August 26, 1998) was an American physicist. He was awarded the 1995 Nobel Prize in Physics for his co-detection of the neutrino with Clyde Cowan in the neutrino experiment. He may be the only scientist in ...

({{subatomic particle, electron neutrino, link=yes, 1956) , Solved the problem of energy

spectrum A spectrum (: spectra or spectrums) is a set of related ideas, objects, or properties whose features overlap such that they blend to form a continuum. The word ''spectrum'' was first used scientifically in optics to describe the rainbow of co ...

beta decay In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which an atomic nucleus emits a beta particle (fast energetic electron or positron), transforming into an isobar of that nuclide. For example, beta decay of a neutron ...

. , - ,

s
({{subatomic particle, up quark, {{subatomic particle, down quark, {{subatomic particle, strange quark) , elementary ,

Murray Gell-Mann Murray Gell-Mann (; September 15, 1929 – May 24, 2019) was an American theoretical physicist who played a preeminent role in the development of the theory of elementary particles. Gell-Mann introduced the concept of quarks as the funda ...

George Zweig George Zweig (; born May 30, 1937) is an American physicist of Russian-Jewish origin. He was trained as a particle physicist under Richard Feynman. He introduced, independently of Murray Gell-Mann, the quark model (although he named it "aces"). ...

(1964) , colspan=2 {{No particular confirmation event for the

quark model In particle physics, the quark model is a classification scheme for hadrons in terms of their valence quarks—the quarks and antiquarks that give rise to the quantum numbers of the hadrons. The quark model underlies "flavor SU(3)", or the Eig ...

. , - ,

charm quark The charm quark, charmed quark, or c quark is an elementary particle found in composite subatomic particles called hadrons such as the J/psi meson and the charmed baryons created in particle accelerator collisions. Several bosons, including th ...

{{subatomic particle, charm quark , elementary (quark) , Sheldon Glashow,

John Iliopoulos John (Jean) Iliopoulos (Greek language, Greek: Ιωάννης Ηλιόπουλος; 1940) is a Greeks, Greek physicist. He is the first person to present the Standard Model of particle physics in a single report. He is best known for his predictio ...

, Luciano Maiani (1970) , B. Richter, S. C. C. Ting ({{SubatomicParticle, J/psi, link=yes, 1974) , , - ,

bottom quark The bottom quark, beauty quark, or b quark, is an elementary particle of the third generation. It is a heavy quark with a charge of − ''e''. All quarks are described in a similar way by electroweak interaction and quantum chromodynamic ...

{{subatomic particle, bottom quark , elementary (quark) , Makoto Kobayashi, Toshihide Maskawa (1973) ,

Leon M. Lederman Leon Max Lederman (July 15, 1922 – October 3, 2018) was an American experimental physicist who received the Nobel Prize in Physics in 1988, along with Melvin Schwartz and Jack Steinberger, for research on neutrinos. He also received the Wolf Pr ...

({{SubatomicParticle, Upsilon, link=yes, 1977) , , - ,

gluon A gluon ( ) is a type of Massless particle, massless elementary particle that mediates the strong interaction between quarks, acting as the exchange particle for the interaction. Gluons are massless vector bosons, thereby having a Spin (physi ...

s , elementary (quantum) , Harald Fritzsch,

(1972) ,

DESY DESY, short for Deutsches Elektronen-Synchrotron (English: ''German Electron Synchrotron''), is a national research centre for fundamental science located in Hamburg and Zeuthen near Berlin in Germany. It operates particle accelerators used to ...

(1979) , , - , weak gauge bosons {{SubatomicParticle, W boson+-, {{SubatomicParticle, Z boson0 , elementary (quantum) , Sheldon Glashow,

Steven Weinberg Steven Weinberg (; May 3, 1933 – July 23, 2021) was an American theoretical physicist and Nobel laureate in physics for his contributions with Abdus Salam and Sheldon Glashow to the unification of the weak force and electromagnetic inter ...

, Abdus Salam (1968) ,

CERN The European Organization for Nuclear Research, known as CERN (; ; ), is an intergovernmental organization that operates the largest particle physics laboratory in the world. Established in 1954, it is based in Meyrin, western suburb of Gene ...

(1983) , Properties verified through the 1990s. , - ,

top quark The top quark, sometimes also referred to as the truth quark, (symbol: t) is the most massive of all observed elementary particles. It derives its mass from its coupling to the Higgs field. This coupling is very close to unity; in the Standard ...

{{subatomic particle, top quark , elementary (quark) , Makoto Kobayashi, Toshihide Maskawa (1973) ,

Fermilab Fermi National Accelerator Laboratory (Fermilab), located in Batavia, Illinois, near Chicago, is a United States Department of Energy United States Department of Energy National Labs, national laboratory specializing in high-energy particle phys ...

(1995) , Does not hadronize, but is necessary to complete the Standard Model. , - ,

, elementary (quantum) , Peter Higgs (1964) , CERN (2012) , Only known spin zero elementary particle. , - , tetraquark , composite , {{dunno , Z_c(3900), 2013, yet to be confirmed as a tetraquark , A new class of hadrons. , - ,

pentaquark A pentaquark is a human-made subatomic particle, consisting of four quarks and one antiquark bound together; they are not known to occur naturally, or exist outside of experiments specifically carried out to create them. As quarks have a bar ...

, composite , {{dunno , colspan=2 , Yet another class of hadrons. {{As of, 2019 several are thought to exist. , - ,

, elementary (quantum) , Albert Einstein (1916) , , Interpretation of a

gravitational wave Gravitational waves are oscillations of the gravitational field that Wave propagation, travel through space at the speed of light; they are generated by the relative motion of gravity, gravitating masses. They were proposed by Oliver Heaviside i ...

as particles is controversial. , - ,

magnetic monopole In particle physics, a magnetic monopole is a hypothetical particle that is an isolated magnet with only one magnetic pole (a north pole without a south pole or vice versa). A magnetic monopole would have a net north or south "magnetic charge". ...

, elementary (unclassified) , Paul Dirac (1931){{cite journal , last1=Dirac , first1=Paul A. M. , date=1931 , title=Quantised singularities in the electromagnetic field , url=https://royalsocietypublishing.org/doi/10.1098/rspa.1931.0130 , journal=Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character , language=en , volume=133 , issue=821 , pages=60–72 , bibcode=1931RSPSA.133...60D , doi=10.1098/rspa.1931.0130 , issn=0950-1207, url-access=subscription , {{not yet, ''hypothetical''{{cite journal , last1=Navas , first1=S. , last2=Amsler , first2=C. , last3=Gutsche , first3=T. , last4=Hanhart , first4=C. , last5=Hernández-Rey , first5=J. J. , last6=Lourenço , first6=C. , last7=Masoni , first7=A. , last8=Mikhasenko , first8=M. , last9=Mitchell , first9=R. E. , last10=Patrignani , first10=C. , last11=Schwanda , first11=C. , last12=Spanier , first12=S. , last13=Venanzoni , first13=G. , last14=Yuan , first14=C. Z. , last15=Agashe , first15=K. , date=2024-08-01 , title=Review of Particle Physics , url=https://link.aps.org/doi/10.1103/PhysRevD.110.030001 , journal=Physical Review D , language=en , volume=110 , issue=3 , page=030001 , doi=10.1103/PhysRevD.110.030001 , issn=2470-0010, hdl=20.500.11850/695340 , hdl-access=free {{rp, loc=25 , {{portal, Physics

References

{{Reflist, refs= There was early debate on what to name the proton as seen in the follow commentary articles b
Soddy 1920
an
Lodge 1920

External links

{{Commons category, Subatomic particles
University of California: Particle Data Group.
{{Particles Subatomic particles Quantum mechanics

Classification

By composition

Hadrons

By statistics

By mass

By decay

Other properties

Dividing an atom

History

See also

References

Further reading

General readers

Textbooks

External links