In science, particle is a small point-sized entity, of which there are three varieties: fundamental particles (or elementary particles), composite particles, and bound state particles, all of which, according to Louis de Broglie, exhibit wave-particle duality.

Discovery timeline
See main: Particle discovery timeline
The follow table shows a work-in-progress timeline of particle discovery: [3]

Predicted / Proposed
Discovered / Identified




Leucippus (c.460BC)Jean Perrin (1909)
Electrone−, β− ½James Stoney (1874)J.J. Thomson (1897)
Alpha particleα, He²⁺, α²⁺
N/AErnest Rutherford (1899)
Photonγ1N/AAlbert Einstein (1905)

N/AErnest Rutherford (1909/1911)
Protonp, p+, N+½William Prout (1815)Ernest Rutherford (1919)
Neutronn, n⁰, N⁰½Ernest Rutherford (1920)James Chadwick (1932)
Paul Dirac (1927); Ettore Majorana (1928)Carl Anderson (1932)
Electron neutrinoνe½Wolfgang Pauli (1930)Frederick Reines and Clyde Cowan (1956)

Paul Dirac (1931)[Unconfirmed]
Graviton G2Dmitrii Blokhintsev and F. M. Gal'perin (1934)[Unconfirmed]
Pionπ+, π⁰, π−0 Hideki Yukawa (1935) Cecil Powell, et al (1947)
Gluon g1Murray Gell-Mann (1962)PLUTO detector (1979)
Up quarku½Murray Gell-Mann (1964); George Zweig (1964)SLAC (1968)
Down quarkd½Murray Gell-Mann (1964); George Zweig (1964)SLAC (1968)
Higgs bosonH⁰0Peter Higgs (1964)CERN LHC (2012)

Murray Gell-Mann and George Zweig (1964) SLAC (1969)
J/ψ (J/Psi) meson

James Bjorken and Sheldon Glashow (1964) Burton Richter and Samuel Ting (1974)
W bosonW−1Sheldon Glashow, Abdus Salam, and Steven WeinbergCERN (1983)
Z bosons Z1Sheldon Glashow, Abdus Salam, and Steven WeinbergCERN (1983)

The standard model, as of 2009, contains 61 elementary particles: 24 fermions, 24 antifermions, 12 vector bosons, and the Higgs boson, grouped as follows: [4]
elementary particles (61)

The following is a basic particle diagram:
Particles (2012, CERN)


Particles can be Fundamental particles are defined as those that do not have an internal structure, whereas composite particles and bound state particles do. Particles can also be classified as either a fermion (leptons, quarks, and baryons), those with half-integer spin, or a boson (gauge bosons and mesons), those with integer spin. All structures in the universe are believed to be comprised of fundamental particles, i.e. composite particles and bound state particles (as well as all other structures) are aggregates of fundamental particles. The following overview table shows the classifications in which the various structures of the universe can be divided: [1]

Fundamental Particles
Composite Particles
Bound State Particles
Leptons and quarks form matter, while gauge bosons carry forces. Quarks feel the strong force, but leptons do not:
Leptons and quarks

These are force-carrier particles. Some shown are hypothetical:
Gauge bosons

Most particles have an antimatter equivalent that has the same mass, but whose charge and other properties are opposite:
Composite particles
The term 'bound state' tends to be used to refer to objects, larger in size than the hydrogen atom, considered as a single entity, particularly in cases where the term 'molecule' is not employable.

Virus (200px)MICROBES
Small motile entities, such as the avian flu virus (adjacent), having an approximate molecular formula of CE3HE3OE4NE4PE2SE2Ca50K50, can be viewed as a bound state of thousands of atoms.

human (particle)PEOPLE
In statistical mechanics, humans, which have a measured 26-element human molecular formula, are often modeled as 'human particles', treated in mass, statistically, to discern bulk behaviors, being quantified as a type of social physics or human physics.

Family (bound state) (f)FAMILIES
Three human molecules, MxFyBc, attached in the tight unit of a bound state family held together via force carrier particles called photons.

Milky Way (200px)GALAXIES
Large aggregated galactic-sized structures, such as the milky way (adjacent), can be considered as a bound state of stars (e.g. sun molecule) and planets (e.g. earth molecule).

The subjects of statistical mechanics and statistical thermodynamics, as mentioned, typically study systems whose entities (atoms, ions, molecules, chemical species , proteins, human molecules, etc.) are modeled as discrete point-sized particles, assumed to have no inter-particle interaction, i.e. adhere to the Boltzmann chaos assumption. When people are modeled as point-sized particles, the subject becomes human statistical mechanics (or human statistical thermodynamics) as contrasted with human chemical thermodynamics, which views people as human molecules, and takes into account aspects such as bond energies, activation energies, free energy coupling, and other energies of interaction. [2]

See also
Field particle
● Messenger particle (or force carrier)
Primary field particle
Secondary field particle
Human particle
● Human particle map

1. Rees, Martin. (2005). Universe (pg. 31). DK Publishing.
2. (a) Thims, Libb. (2007). Human Chemistry (Volume One). Morrisville, NC: LuLu.
(b) Thims, Libb. (2007). Human Chemistry (Volume Two). Morrisville, NC: LuLu.
3. Timeline of particle discoveries – Wikipedia.
4. Braibant, Sylvie, Giacomelli, Giorgio, and Spurio, Maurizio. Particles and Fundamental Interactions: An Introduction to Particle Physics (2009). (pg. 314). Springer.

External links
Elementary particles – Wikipedia.
List of particles – Wikipedia.

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