Fundamental Particles (CIE A Level Physics)

• Quarks are fundamental particles that make up other subatomic particles such as protons and neutrons
• Protons and neutrons are in a category of particles called hadrons
  • Hadrons are defined as any particle made up of quarks

• Fundamental means that the particles are not made up of any other particles
• Quarks have never been observed on their own, they are either in pairs or groups of three
• There are six flavours (types) of quarks that exist:
  • up
  • down
  • charm
  • strange
  • top
  • bottom

The six flavours of quarks

The six flavours of quarks are up, down, charm, strange, top and bottom

• Leptons are also a group of fundamental (elementary) particles
• This means they are not made up of any other particles (no quarks)
• There are six leptons altogether:
  • electron
  • electron neutrino
  • muon
  • muon neutrino
  • tau
  • tau neutrino

The six leptons

 

The six leptons are all fundamental particles

• The muon and tau particle are very similar to the electron but with slightly larger mass
• Electrons, muon and tau particles all have a charge of -1e 
• There are three flavours (types) of neutrinos (electron, muon, tau)
• Neutrinos are the most abundant leptons in the universe
  • They have no charge and negligible mass (almost 0)

• Leptons interact with the weak interaction, electromagnetic and gravitational forces
• However, they do not interact with the strong force
• Although quarks are fundamental particles too, they are not classed as leptons
• Leptons do not interact with the strong force, whilst quarks do