Particles and Radiation

• Atom


  Formed of 3 constituents: protons, neutrons and electrons
• Nucleus


  Formed of protons and neutrons, also known as nucleons
• Electrons


  Orbit the nucleus in shells
• Particle properties


  • Charge (C)
  • Relative Charge
  • Mass (kg)
  • Relative Mass
  • Specific Charge (C/kg)

  
• Proton


  Charge: +1.6 x 10^-19 C, Relative Charge: +1, Mass: 1.67 x 10^-27 kg, Relative Mass: 1, Specific Charge: 9.58 x 10^7 C/kg
• Neutron


  Charge: 0, Relative Charge: 0, Mass: 1.67 x 10^-27 kg, Relative Mass: 1, Specific Charge: 0 C/kg
• Electron


  Charge: -1.6 x 10^-19 C, Relative Charge: -1, Mass: 9.11 x 10^-31 kg, Relative Mass: 0.0005, Specific Charge: 1.76 x 10^11 C/kg

  
• Specific charge


  Charge-mass ratio of a particle

  
• Proton number (Z)


  Number of protons in an atom
• Nucleon number (A)


  Number of protons and neutrons in an atom
• Isotopes


  Atoms with the same number of protons but different numbers of neutrons
• Carbon-14


  Radioactive isotope of carbon used in carbon dating
• Carbon dating


  Calculating the approximate age of an object containing organic material by measuring the percentage of carbon-14 remaining
• Strong nuclear force (SNF)


  Keeps nuclei stable by counteracting the electrostatic force of repulsion between protons
• The SNF is attractive up to separations of 3 fm, but repulsive below separations of 0.5 fm
• Unstable nuclei


  Have too many of either protons, neutrons or both, causing the SNF to not be enough to keep them stable
• Alpha decay


  1. Proton number decreases by 2

  2. Nucleon number decreases by 4
• Beta-minus decay


  1. Proton number increases by 1

  2. Nucleon number stays the same
• Energy was not conserved in beta-minus decay, leading to the discovery of neutrinos
• Antiparticle


  Has the same rest energy and mass but all other properties are opposite the particle
• Particle properties


  • Mass (kg)
  • Rest energy (MeV)
  • Charge (C)
• Electron neutrino


  Mass: 0 kg, Rest energy: 0 MeV, Charge: 0 C
• Electron antineutrino


  Mass: 0 kg, Rest energy: 0 MeV, Charge: 0 C
• Photon


  Electromagnetic radiation that travels in packets and transfers energy, has no mass
• Energy of photons


  Directly proportional to the frequency of electromagnetic radiation, E = hf
• Annihilation


  A particle and its corresponding antiparticle collide, their masses are converted into energy released as 2 photons
• PET scanner


  Uses annihilation of positrons and electrons to produce 3D images of the inside of the body
• Pair production


  A photon is converted into an equal amount of matter and antimatter
• Fundamental forces


  • Gravity
  • Electromagnetic
  • Weak nuclear
  • Strong nuclear
• Exchange particles


  Carry energy and momentum between particles experiencing a force
• Exchange particles for each force


  • Gravity: Graviton (not on specification)

  Electromagnetic: Virtual photon (γ)

  Weak: W boson (W+ or W-)

  Strong: Gluon
• Electron capture


  p + e- → n + νe
• Electron-proton collision


  p + e- → n + νe
• Beta-plus decay


  p → n + e+ + νe
• Beta-minus decay


  n → p + e- + νe
• Hadrons


  Particles formed of quarks that experience the strong nuclear force
• Leptons


  Fundamental particles that do not experience the strong nuclear force
• Types of hadrons


  • Baryons (formed of 3 quarks)

  Antibaryons (formed of 3 antiquarks)

  Mesons (formed of a quark and antiquark)
• Baryon number


  Shows whether a particle is a baryon (1), antibaryon (-1), or not a baryon (0)
• Baryon number is always conserved in particle interactions