Half-life

• What is the purpose of radioactive isotopes?

  Used for blood flow monitoring and cancer treatment
• What does the term 'half-life' refer to?

  The time taken for half of the nuclei to decay
• What happens during radioactive decay?

  An unstable nucleus emits an alpha or beta particle
• What is the outcome of radioactive decay?

  The nucleus transforms into a new element
• How does the decay model illustrate the process of radioactive decay?

  Green squares decay into red squares over time
• What does the decay curve represent?

  The pattern of parent nuclei halving over time
• What does the term 'activity' refer to in radioactivity?

  The number of decays per second of a radioactive element
• How is activity measured?

  In becquerels (Bq)
• What does 1 Bq represent?

  1 decay per second
• How can activity be represented in exam questions?

  As counts per second or counts per minute
• What is a Geiger counter used for?

  To register decays as clicks or counts
• What are the key concepts of radioactive half-life?

  • Time for half of parent nuclei to decay
  • Random process of decay
  • Activity measured in becquerels (Bq)
  • Decay curve shows halving pattern
• What are the applications of radioactive isotopes?

  • Blood flow monitoring
  • Cancer treatment
  • Carbon dating
  • Smoke alarms
• What is the relationship between parent and daughter nuclei in radioactive decay?

  • Parent nuclei decay into daughter nuclei
  • Random decay process
  • Half of parent nuclei decay over each half-life
• What are some applications of radioactive isotopes?

  Blood flow monitoring, cancer treatment, carbon dating
• What is a characteristic of each radioactive isotope used in applications?

  Each has a specific half-life
• What are the half-lives of common isotopes used in GCSE questions?

  • Thorium-232: 14,000 million years
  • Uranium-235: 704 million years
  • Plutonium-239: 24,110 years
  • Carbon-14: 5,730 years
  • Caesium-137: 30 years
  • Cobalt-60: 5.27 years
  • Polonium-210: 138 days
  • Technetium-99m: 6 hours
  • Polonium-218: 3 minutes
• What is the half-life of Cobalt-60?

  5.27 years
• What is the half-life of Carbon-14?

  5,730 years
• What happens to the mass of cobalt-60 every 5.27 years?

  The mass halves
• How does the activity of carbon-14 change over time?

  It halves every 5,730 years
• If an isotope has a half-life of 6 days, what happens after 6 days?

  The number of parent nuclei halves
• How many half-lives are needed for a 2 g sample to decay to 0.25 g if the half-life is 27 years?

  Three half-lives
• How long will it take for a 2 g sample to decay to 0.25 g with a half-life of 27 years?

  81 years
• If an isotope's activity falls from 600 Bq to 150 Bq in 10 days, what is its half-life?

  5 days
• How long will it take for 8,000 nuclei to decay to below 200 if the half-life is 30 years?

  Between 150 and 180 years
• How many half-lives are needed for 8,000 nuclei to decay to 250 nuclei?

  Five half-lives
• How many half-lives are needed for 8,000 nuclei to decay to 125 nuclei?

  Six half-lives
• What is the process of using a decay curve to find the half-life?

  1. Plot the decay data on a graph
  2. Identify the time it takes for the quantity to halve
  3. Repeat for accuracy
  4. Determine the half-life from the graph
• What are the key concepts of radioactive decay?

  • Half-life: time for half the substance to decay
  • Activity: rate of decay measured in Bq
  • Parent nuclei: original radioactive atoms
  • Decay products: stable or unstable isotopes formed
• What is the purpose of radioactive isotopes?

  Used for blood flow monitoring and cancer treatment
• What does each radioactive isotope have?

  A characteristic half-life
• What are some applications of radioactive isotopes?

  • Blood flow monitoring
  • Cancer treatment
  • Paper mills
  • Carbon dating
  • Smoke alarms
• How do you find the half-life from a decay curve?

  By observing the activity change over time
• If the starting activity is 80 counts per minute, what is half of that?

  40 counts per minute
• What is the half-life of the second isotope mentioned?

  1.3 billion years
• How can you estimate the half-life of an isotope?

  By analyzing the decay curve
• What are the steps to find the half-life from a decay curve?

  1. Identify the starting activity.
  2. Determine half of the starting activity.
  3. Locate this value on the graph.
  4. Measure the time taken to reach this value.
• What are some applications of radioactive isotopes?

  Blood flow monitoring, cancer treatment, carbon dating
• What is a characteristic of each radioactive isotope?

  Each has a specific half-life