Fundamental ParticlesFundamental Particles

Each particle has a corresponding antiparticle with the same mass but opposite values for all other properties (e.g. strangeness, charge). Examples of particle-antiparticle pairs include: electron-positron, proton-antiproton, neutronantineutron, neutrino-antineutrino.                                                                    


  1. Composed of quarks so not fundamental
  2. Subject to strong nuclear force
  3. Baryons and mesons 4. g. protons and neutrons


  1. Fundamental
  2. Subject to weak nuclear force
  3. Electrons and neutrinos

The quark model of hadrons proposes that hadrons consist of a combination of 6 quarks: up, down, top, bottom, strange and charm (and their respective antiquarks). 

Quark                Charge / e      Strangeness

Up                            +frac{2}{3}                    0

Down                      −(1/3)                  0

Strange                   −(1/3) 

The antiparticles of these quarks have the opposite charge and strangeness, but the same mass. Protons are uud; neutrons are udd. 

There are four fundamental forces in nature:

Fundamental force Effect Relative strength Range (m)
Strong nuclear On nucleons 1 ~10-15
Electromagnetic On charged particles 10-3 Infinite
Weak nuclear Responsible for β-decay 10-6 ~10-18
Gravitational On all particles with mass 10-40 Infinite 


Beta decay is the emission of electrons or positrons. The force responsible for it is the weak nuclear force. It involves changes to neutrons or protons.

  1. 10n → 11p + −01e + ̅
  2. This can be explained in terms of quark transformations: d → u + 01e + ̅ β+ decay:
  3. 10p → 11n + +01e +
  4. This can be explained in terms of quark transformations: u → d + +01e +

In both cases, charge is conserved.