6.4 - Nuclear and particle physics

• What is the nucleon number

  Number of protons and neutrons (particles) in the nucleus

  Where A represent the nucleon number

  
• What does z represent

  The proton number

  
• How to work out number of neutrons

  Nucleon number - proton number
• What conclusions did Rutherford make about the nuclear model

  Only 1 in 8000 alpha particles are reflected meaning most of the atom is a vacuum (empty space)

  They can deflect a fast moving alpha particle meaning the mass is concentrated in the middle

  They repel positive alpha particles meaning the mass is positively charged

  Negative charges are needed to keep the atom neutral meaning small negative electrons are spread thinly around
• Ion


  An atom that has lost one or more electrons to give it a positive net charge
• Specific charge of an ion

  Charge to mass ratio of an ion
• Isotope

  Different masses of the same element; has same number of protons and different number of neutrons
• Electron scattering

  The diffraction of electrons by nuclei - wave/particle duality gives a pattern of minima and maxima
• Rest mass energy of particles

  The energy required to create the particle

  Calculate using E=mc²
• Nuclear forces

  Forces that act on quarks
• Antimatter

  Particles that have the same mass but all the opposite quantum properties
• Pair creation

  The energy of a photon, when released to create a particle and its antiparticle
• Leptons

  Fundamental matter particles not affected by the nuclear strong force
• Hadrons

  A class of sub atomic particles that experience the nuclear strong force
• Exchange particles

  Virtual particles that cause interactions by transferring energy/momentum
• Equation for wavelength of electrons 


  h / sqrt(2qmV)
• Strangeness of strange quark

  -1
• Strangeness of strange antiquark

  1
• Baryon number of quarks

  1/3
• Baryon number of antiquarks

  -1/3
• Strangeness of up and down quarks and antiquarks

  0
• How to find the relative charge of antiquarks

  Same as quarks but the sign is switched

  Eg charge of up quark is 2/3 so charge of up antiquark is -2/3
• What is an anti electron called

  Positron
• Why are elements with more neutrons than protons more stable

  More neutrons means that all nucleons feel the nuclear strong force attraction. It also means all the protons feel less electromagnetic repulsive forces; since neutrons are uncharged they do not contribute to the electromagnetic repulsion
• Formula for density of nucleus

  3Au/4piR³

  Where A is the nucleon number

  Where u is the unified mass
• Unified mass

  The average mass of particles
• What does the alpha-scattering experiment show?

  Small, dense nucleus as few alpha particles are refracted Positive nucleus Mostly empty space
• Nuclear strong force

  Force that holds the nucleus together overcomes the electrostatic force of repulsion between protons
• Type of hadrons

  Baryons ( three quarks) Mesons (two quarks - quark and

  antiquark)
• Example of baryons

  Proton

  Neutron
• 4 fundamental forces

  Nuclear strong force

  Nuclear weak force

  Electromagnetic

  Gravity
• Which of the fundamental forces do hadrons experience

  All four
• 3 types of quarks

  Up

  Down

  Strange
• 3 types of leptons

  Electron

  Muon

  Neutrino
• 6 types of mesons

  Pion plus

  Pion minus

  Pion zero

  Kaon plus

  Kaon minus

  Kaon zero
• What must be conserved during decay?

  Q - charge

  B - baryon number

  L - lepton number

  S - strangeness
• Alpha particle

  Positively charged particles that contains 2 protons and 2 neutrons
• Annihilation 


  When a particle and its antiparticle meet, they annihilate each other andrelease two gamma photons. They are released in order to conserve momentum. The mass of the particles will transform into the energy equivalent
• What is a meson

  Unstable particles made of a quark and an antiquark
• Exchange particles for the nuclear strong force and what if act upon

  Pions

  Acts on hadrons