Fermion

Key Stage 5

Meaning

Fermions are a group of subatomic particles which are not able to exist in the same place at the same time as one another.

NB: This definition is loose and inaccurate, but sufficient at this stage. It is more accurate to state that they are 'half-integer spin' and unable to have the same 'quantum state' as one another.

About Fermions

Subatomic particles are divided into two major categories; fermions and bosons. Bosons, in contrast to fermions, can exist in the same place at the same time as one another.

The fermions include:

• Leptons - A group of fundamental particles
  • Electron - A type of lepton with a mass of 9.11x10^-31 and a charge of -1.60x10^-19.
  • Muon - A type of lepton often referred to as a 'heavy electron' same charge as an electron (-1.60x10^-19) but a mass 206 times the mass of an electron.
  • Neutrino - A type of lepton with zero charge and negligible mass.
• Quarks - A group of subatomic particles believed to be fundamental but have never been observed on their own. They always exists in either a triplet of quarks or a quark-antiquark pair. (NB: A quark-antiquark pair known as a meson is a type of boson.)
• Hadrons - Subatomic particles made of quarks.
  • Baryons - A type of hadron made of 3 quarks.
    • Proton - A type of baryon with a mass of 1.67x10^-27 and a charge of 1.60x10^-19, made of 2 Up-quarks and 1 Down-quark.
    • Neutron - A type of baryon with a mass of 1.67x10^-27 and zero charge, made of 2 Down-quarks and 1 Up-quark.