Topic 6-Radioactivity

• What is the charge of a proton?

  +1
• What is the charge of a neutron?

  0
• What is the charge of an electron?

  -1
• What is the relationship between protons and electrons in a neutral atom?

  They have the same number
• What is the size of an atom?

  ~0.1 nanometers
• What defines isotopes of an element?

  Same protons, different neutrons

  
• What is the mass number represented by in isotopes?

  A
• What does Z represent in isotopes?

  Proton number
• What happens when electrons absorb EM radiation?

  They move to a higher orbit
• What occurs when electrons emit EM radiation?

  They fall to a lower orbit
• What is alpha decay?

  Emission of a helium nucleus
• How penetrating is alpha radiation?

  Weakly penetrating
• What is beta minus decay?

  Neutron becomes a proton, releases an electron
• What is gamma radiation?

  Electromagnetic radiation
• What is background radiation?

  Weak radiation from natural sources
• What does a Geiger-Muller tube do?

  Detects radiation and produces clicks
• Who discovered the electron?

  JJ Thomson
• What did Rutherford's Gold Foil Experiment demonstrate?

  Most of the atom is empty space
• What is the overall charge of an atom?

  Neutral
• What happens to alpha particles in the Gold Foil Experiment?

  Some are deflected, most pass through

  
• What is beta plus decay?

  Proton becomes a neutron, releases a positron
• What is the unit of activity in radioactivity?

  Becquerel, Bq
• What is half-life?

  Time for half nuclei to decay
• How does the activity of a radioactive sample change over time?

  It decreases exponentially
• How do you calculate net decline after X half-lives?

  Initial number minus number after X half-lives
• What is the net decline after 3 half-lives from 80 nuclei?

  70/80
• What are the uses of radioactivity?

  • Smoke alarms using Americium
  • Irradiating food to kill bacteria
  • Sterilisation of equipment
  • Tracing and gauging thickness
  • Diagnosis and treatment of cancer
• What are the dangers of ionising radiation?

  • Short half-life: Less long-term risk
  • Long half-life: More long-term risk
• What is the half-life of Americium used in smoke alarms?

  432 years
• How does gamma radiation sterilize food?

  Kills bacteria by transferring energy
• How is beta radiation used in gauging thickness?

  Measures thickness by detecting electrons
• What is the effect of gamma rays on cancer cells?

  They kill cancer cells
• What is the risk of exposing healthy cells to gamma rays?

  Possible mutation or damage
• What happens to the activity of a radioactive sample over time?

  It decreases exponentially
• What is the significance of a short half-life in radioactive sources?

  Less long-term risk due to quick decay
• What is the significance of a long half-life in radioactive sources?

  More long-term risk due to slow decay
• What is the role of alpha particles in smoke alarms?

  Ionise air particles to create current
• How does smoke affect the current in a smoke alarm?

  It drops the current in the circuit
• What is the purpose of using beta radiation in pipes?

  To measure the thickness of pipe walls
• What happens to nuclei after decay?

  They often release gamma radiation