Atoms & Nuclear Radiation

• What is the main reason some atomic nuclei are unstable?


  Imbalance in the forces within the nucleus
• What is an example of an unstable isotope of carbon?


  Carbon-14
• Why is carbon-14 considered unstable compared to carbon-12?


  Because carbon-14 has two extra neutrons
• What can cause some isotopes to be unstable?


  Large size or having too many or too few neutrons
• What happens to unstable nuclei during radioactive decay?


  They emit radiation to become more stable
• What is the process of emitting radiation from unstable nuclei called?


  Radioactive decay
• How does radiation affect the energy of the nucleus?


  It reduces the overall energy of the nucleus
• How is activity defined in the context of radioactive decay?

  The rate at which unstable nuclei from a source of radiation decays
• What unit is used to measure activity in radioactive decay?

  Becquerels (Bq)
• What does 1 Becquerel represent?


  1 nucleus in the source decaying in 1 second
• If a source of radiation has an activity of 2000 Bq, how many unstable atoms decay in 2 minutes?


  240,000 unstable nuclei decay in 2 minutes
• What is the purpose of a Geiger-Muller tube?


  To detect radiation
• How does a Geiger counter work?


  It counts the ions created in the Geiger-Muller tube
• What is count-rate in the context of radiation detection?


  The number of decays recorded each second by a detector
• If a Geiger-Muller tube counts 16,000 decays in 1 hour, what is the count rate?

  1. 5 decays per second
• What is the difference between activity and count rate?

  Activity is the rate at which unstable nuclei decay, while count rate is the rate at which radioactive emissions are detected
• What types of radiation can be emitted from unstable nuclei?

  Alpha particles, beta particles, gamma waves, and neutrons
• Which type of radiation is the least penetrating?

  Alpha radiation
• What material can stop alpha particles?


  Paper
• What material can stop beta particles?


  A few millimeters of aluminium
• How does gamma radiation interact with materials?

  Gamma can pass through aluminium and is only partially stopped by thick lead
• What happens when an atom is ionised?


  The number of electrons it has changes, giving it a non-zero charge
• Which type of radiation is the most ionising?

  Alpha radiation
• Which type of radiation is the least ionising?

  Gamma radiation
• How does the range of radiation in air relate to its ionising power?


  The more ionising a form of radiation is, the shorter its range in air
• How far does alpha radiation travel in air?


  A few centimetres
• How far does beta radiation travel in air?

  A few tens of centimetres
• What is the range of gamma radiation in air?


  Infinite range
• What are some uses of radiation?


  • Producing electricity through nuclear fission
  • Medical procedures including diagnosis and treatment
  • Testing material
  • Determining the age of ancient artefacts
  • Checking the thickness of materials
  • Smoke detectors
• Why are alpha particles used in smoke detectors?


  • Alpha radiation ionises the air within the detector, creating a current
  • Smoke blocks the alpha emitter
  • The alarm is triggered when the sensor no longer detects alpha
• What occurs during alpha decay?

  An alpha particle is emitted from an unstable nucleus
• What is an alpha particle composed of?


  2 protons and 2 neutrons
• What happens to the mass number and atomic number during alpha decay?


  The mass number decreases by 4 and the atomic number decreases by 2
• What is the significance of decay equations?


  They show the particles present before and after the decay
• What occurs during beta decay?


  A neutron changes into a proton and an electron is emitted
• What happens to the mass number and atomic number during beta decay?


  The mass number stays the same, but the atomic number increases by one
• What occurs during gamma decay?


  A gamma ray is emitted from an unstable nucleus
• How does gamma decay affect the mass number and atomic number?


  It does not affect the mass number or atomic number
• What is the nature of radioactive decay?


  It is a random process.
• Why can't we predict when a particular unstable nucleus will decay?


  Because radioactive decay is a random process.