The 17 particles
According to the Standard Model, all matter is made of six quarks and six leptons. A proton is two up quarks and one down quark, a neutron one up and two down, and the electron orbiting atoms is a lepton. Quarks and leptons come in three generations of increasing mass, and nearly all everyday matter is built from the first. Add four force-carrying gauge bosons and the Higgs boson, which gives other particles mass, and you have 17 kinds. Each also has an antiparticle with opposite charge.
| Group | Particles | Notes |
|---|---|---|
| Quarks (6) | Up, down, charm, strange, top, bottom | Feel the strong force; build protons and neutrons |
| Leptons (6) | Electron, muon, tau and three neutrinos | Do not feel the strong force |
| Gauge bosons (4) | Photon, gluon, W boson, Z boson | Carry electromagnetic, strong and weak forces |
| Scalar boson (1) | Higgs boson | Discovered at CERN in 2012 |
How it was built
Sheldon Glashow in 1961 and Steven Weinberg and Abdus Salam in 1967 unified electromagnetism with the weak force behind radioactive decay into electroweak theory. In 1964 Murray Gell-Mann and George Zweig explained hundreds of hadrons as combinations of a few quarks, and in 1973 David Gross, Frank Wilczek and David Politzer completed quantum chromodynamics, the theory of the strong force that binds quarks. The W and Z bosons were found in 1983, the top quark in 1995 and the tau neutrino in 2000; in 2012 CERN's Large Hadron Collider found the last piece, the Higgs boson. The model predicts the electron's magnetic moment to more than ten decimal places, making it one of the most precisely tested theories in science.
Limits of the Standard Model
Even so, it is not a final theory. It leaves out gravity, the fourth fundamental force, so it sits apart from general relativity, which explains gravitational waves and black holes. It contains no particle for dark matter, about 85% of the matter in the universe, nor for the dark energy accelerating cosmic expansion. Neutrinos are massless in the original model, yet Japan's Super-Kamiokande showed in 1998 that they have tiny masses, and the model does not fully explain why matter outlasted antimatter after the Big Bang. Physicists look beyond it with supersymmetry, grand unified theories and string theory.
FAQ
- Does "model" mean the theory is unproven?
- No. The name is historical; it has been confirmed by countless experiments with extraordinary precision. It is seen as part of a larger theory because it misses gravity and dark matter.
- Are there really only 17 particles?
- Counting antiparticles and quark and gluon colour states separately gives more, but by kind there are 6 quarks, 6 leptons, 4 gauge bosons and 1 Higgs: 17.
Sources reviewed: 2026-10-26
References
- Glashow, S. L. (1961). Partial-symmetries of weak interactions. Nuclear Physics, 22(4), 579–588.
- Weinberg, S. (1967). A model of leptons. Physical Review Letters, 19(21), 1264–1266.
- Gell-Mann, M. (1964). A schematic model of baryons and mesons. Physics Letters, 8(3), 214–215.
- Particle Data Group. (2024). Review of Particle Physics. Physical Review D, 110, 030001.