(2.1) Particles

• What are the three constituents of an atom?

  Protons, neutrons, and electrons
• What forms the nucleus of an atom?

  Protons and neutrons
• What are nucleons?

  Protons and neutrons in the nucleus
• How do electrons move in an atom?

  They orbit the nucleus in shells
• What properties of particles can be described in SI and relative units?

  • Charge (C)
  • Relative Charge
  • Mass (kg)
  • Relative Mass
  • Specific Charge (Ckg^-1)
• What is the charge of a proton in coulombs?

  +1.6 × 10⁻¹⁹ C
• What is the mass of a neutron in kilograms?

  1.67 × 10⁻²⁷ kg
• How is specific charge calculated?

  Charge divided by mass

  
• What is the specific charge of a proton?

  9.58 × 10⁷ Ckg⁻¹

  
• What does the proton number (Z) represent?

  Number of protons in an atom
• What does the nucleon number (A) represent?

  Number of protons and neutrons
• What are isotopes?

  Atoms with the same protons, different neutrons
• What is carbon-14 used for?

  Carbon dating of organic materials
• What is the strong nuclear force (SNF)?

  Force that stabilizes the nucleus
• What does the strong nuclear force counteract?

  Electrostatic force of repulsion
• What is the range of the strong nuclear force?

  Short range, up to 3 fm
• What happens to unstable nuclei?

  They decay to become stable
• What is alpha decay?

  Decay in large nuclei with excess nucleons
• What changes occur during alpha decay?

  Proton number decreases by 2, nucleon number by 4
• What is beta-minus decay?

  Decay in neutron-rich nuclei
• What changes occur during beta-minus decay?

  Proton number increases by 1, nucleon number stays the same
• What was hypothesized to account for energy conservation in beta decay?

  Neutrinos were hypothesized
• What is an antiparticle?

  Particle with opposite properties
• What is the relationship between a particle and its antiparticle?

  Same mass, opposite properties
• What is the mass of an electron?

  9.11 × 10⁻³¹ kg
• What is the energy of a photon proportional to?

  Frequency of electromagnetic radiation
• What is the equation for photon energy?

  E = hf
• What is annihilation in particle physics?

  Collision of particle and antiparticle
• What is produced during annihilation?

  Energy and two photons

  
• How does a PET scanner utilize annihilation?

  Detects gamma photons from positron-electron annihilation
• What is pair production?

  Photon converted into matter and antimatter
• What is required for pair production to occur?

  Photon energy greater than rest energy of particles
• What are the four fundamental forces?

  • Gravity
  • Electromagnetic
  • Weak nuclear
  • Strong nuclear
• What are exchange particles?

  Particles that carry energy and momentum
• What is the exchange particle for the strong force?

  Gluon
• What is the exchange particle for the weak force?

  W boson
• What is the exchange particle for electromagnetic force?

  Virtual photon
• What is the exchange particle for gravity?

  Graviton (not specified)
• What is the weak nuclear force responsible for?

  Beta decay and electron capture
• What is the lepton number of a lepton?

  1