radioactive decay

• What are isotopes?

  Different forms of an element with the same number of protons but different numbers of neutrons
• Why are only one or two isotopes of an element stable?

  Because most isotopes are unstable and undergo radioactive decay
• What does it mean when a material is described as radioactive?

  It consists of unstable isotopes that can decay
• What are the four types of nuclear radiation?

  • Alpha particles
  • Beta particles
  • Gamma rays
  • Neutrons
• What are alpha particles made up of?

  Two protons and two neutrons
• How are alpha particles represented?

  With helium's nuclear symbol, $^{4}_{2}He$
• What is the charge of alpha particles?

  They have an overall charge of +2
• How far can alpha particles travel in the air?

  They can only travel a few centimeters
• What can stop alpha particles?

  A single sheet of paper
• Why are alpha particles strongly ionizing?

  Because they can easily knock electrons off atoms they collide with
• What are beta particles?

  Electrons emitted from a decaying neutron
• What is the charge of beta particles?

  • 1
• How do beta particles penetrate materials?

  They penetrate moderately far into materials
• How much air is needed to stop beta particles?

  Several meters of air
• How much aluminum is needed to stop beta particles?

  About five millimeters
• What are gamma rays?

  Waves of electromagnetic radiation
• Why are gamma rays weakly ionizing?

  Because they have no mass or charge and pass through materials
• How far can gamma rays travel through air?

  They can travel long distances
• What is required to stop gamma rays?

  A thick piece of lead or multiple meters of concrete
• What happens when a nucleus contains too many neutrons?

  It can emit a neutron to increase stability
• Recap the types of radiation and their stopping materials.

  • Alpha particles: stopped by a single sheet of paper
  • Beta particles: stopped by a thin sheet of aluminum
  • Gamma rays: stopped by thick lead or multiple meters of concrete
• What are the two terms discussed in the video related to radioactive materials?

  Activity and half-life
• What is the definition of activity in the context of radioactive materials?

  Activity is the overall rate of decay of all isotopes in a sample.
• In what unit is activity measured?

  Activity is measured in becquerels.
• How many decays per second does an activity of 600 becquerels represent?

  It represents 600 isotopes decaying each second.
• What is half-life in the context of radioactive decay?

  Half-life is the time taken for the number of radioactive nuclei or the activity to halve.
• If a sample has an initial activity of 600 decays per second, what will its activity be after one half-life?

  The activity will be 300 decays per second.
• How does the decay process of radioactive isotopes behave over time?

  • The decay process is random for individual isotopes.
  • As time passes, the number of unstable particles decreases.
  • The overall rate of decay (activity) also decreases.
  • The sample appears to decay more slowly over time.
• What is the relationship between the number of radioactive nuclei and the activity of a sample?

  • Fewer radioactive nuclei result in lower activity.
  • Activity is directly correlated with the number of unstable nuclei.
  • Both definitions of half-life are related to this correlation.
• Why does the activity of a radioactive sample decrease over time?

  Because there are fewer radioactive nuclei left to decay.
• How is the decay process visually represented?

  It is represented by a graph plotting activity in becquerels against time.
• How can you determine the half-life from a decay graph?

  By finding the time it takes for the activity to halve.
• How many half-lives are there in five days if the half-life is 40 hours?

  There are three half-lives in five days.
• If you start with 3 million radioactive nuclei, how many will remain after three half-lives?

  375,000 nuclei will remain.
• What is the purpose of a Geiger-Muller tube?

  To record the decays that reach it each second.
• What device is used to measure the activity of radioactive materials in real life?

  • A Geiger-Muller tube is used.
  • It records decays that reach it each second.
  • It measures alpha, beta, and gamma radiation.
  • The count rate is used to estimate activity.
• What does the count rate from a Geiger-Muller tube indicate?

  The count rate indicates the activity of the radioactive sample.
• What are the two main terms discussed in the video regarding radiation?

  Irradiation and contamination
• What is irradiation?

  Irradiation is the process by which an object is exposed to radiation
• What types of radiation can cause irradiation?

  Both ionizing and non-ionizing radiation can cause irradiation