Three Types of Radioactivity

There are three types of radiation - alpha (α), beta (β) and gamma (γ).

What are alpha, beta and gamma radiation made from? [3]
- Alpha particles: 2 protons and 2 neutrons.
  - What's the difference between an alpha particle and a helium atom ? [1]
    - Alpha particles do not have electrons
  - Are alpha particles larger than the other two types of radiation? [1]
    - Yes - alpha particles are the largest.
  - How do alpha particles ionise and how ionising are alpha particles? [2]
    - They are strongly ionising because they're big, heavy and slow moving
    - they bash into a lot of atoms (with no overall charge) and knock electrons off them, creating a lot of ions (which are charged) - hence the term "ionise".
  - Are alpha particles deflected (direction changed) by electric and magnetic fields? [1]
    - Yes, because they're electrically charged (positively)
- Beta particle: high speed electron
  - Which part of the atom is the beta particle emitted from? [1]
    - the nucleus
  - How does this happen? [1]
    - A neutron turns into a proton and an electron (the beta particle)
  - Are beta particles larger than alpha particles? [1]
    - No. They are quite small and move quite fast
  - How ionising are beta particles? [1]
    - They are moderately ionising
  - Are Beta particles deflected (direction changed) by electric and magnetic fields? [1]
    - Yes because they're electrically charged (negatively)
- Gamma rays: high energy EM wave (or photon)
  - From which part of the atom are gamma rays emitted? [1]
    - nucleus
  - Are gamma rays heavier than alpha particles? [1]
    - No. Gamma rays have no mass.
  - How ionising are gamma rays and why? [2]
    - Weakly ionising
    - Gamma rays tend to pass through rather than collide with atoms. (but eventually they hit something and do damage)
  - Are gamma rays deflected (direction changed) by electric and magnetic fields? [1]
    - No - gamma rays have no electrical charge.
  - Can you get gamma decay along with alpha or beta decay? [1]
    - Yes. Gamma emission always happens after alpha or beta decay. You never get just gamma rays emitted
Which material can block each type of radiation? [3]
- Alpha particles: blocked by paper, skin, few centimetres of air
- Beta particles: blocked by layer of clothing, thin metal (eg aluminium)
- Gamma rays: blocked by thick lead, very thick concrete
A nucleus decays and emits radiation to become more stable - but what makes some nuclei unstable (and hence radioactive) to begin with? [3]
- too many or too few neutrons
  - What type of decay will occur in this situation? [1]
    - Beta decay
  - How will the mass (nucleon) and atomic (proton) number change during this type of decay? [2]
    - or
    - mass (nucleon) number stays the same
    - atomic (proton) number increases by one
- too many protons and neutrons altogether (i.e. it's too heavy)
  - What type of decay will occur in this situation? [1]
    - Alpha decay
  - How will the mass (nucleon) and atomic (proton) number change during this type of decay? [2]
    - mass (nucleon) number decreases by 4
    - atomic (proton) number decreases by 2
- too much energy
  - What type of decay will occur in this situation? [1]
    - Gamma decay
  - How will the mass (nucleon) and atomic (proton) number change during this type of decay? [2]
    - mass (nucleon) number stays the same
    - atomic (proton) number stays the same

Classwork
- 1) Describe the nature and properties of alpha, beta and gamma radiation.
- 2) What is meant by ionisation?
- 3) Which is the most ionising out of alpha, beta and gamma radiation?
- 4) What type of radiation is stopped by paper?
- 5) What substances could be used to block: a) alpha-radiation, b) beta-radiation, c) gamma-radiation?
- 6) Cobalt-60 nuclei lie above the curve of stability. What does this tell you about the number of neutrons in a cobalt-60 nucleus compared to the number of protons?
- 7) What kind of radiation will cobalt-60 emit?
- 8) During Beta decay what happens to the number of protons in the nucleus? What happens to the number of neutrons?
- 9) After alpha (or beta) decay, a nucleus often has too much energy. How does it lose this energy?
- 10) Explain clearly why gamma rays are less ionising than alpha particles
Homework
- 1) Alpha, Beta and gamma are all types of ionising radiation, but they have quite different properties.
  - Rate the different types of radiation according to their penetrating power. ( 1 = high penetrating power, 2 = moderate penetrating power, 3 = low penetrating power )
    - alpha =
    - beta =
    - gamma =
  - How does the penetrating power of each type of radiation compare to its ionising power?
  - Give an example of a material that can stop:
    - alpha radiation
    - beta radiation
- 2) Complete the following sentences about radioactive decay
  - During beta-decay a .......................... becomes a .............................
  - Their atomic number increases by 1 and mass number ......................
  - Alpha and Beta decay all result in the formation of a different ......................, which is shown by the change in ....................... number
- 3) For each section choose the correct word from the brackets to describe: a) alpha, b) beta and c) gamma radiation
  - Ionising Power ( weak / moderate / strong )
  - Charge ( positive / none / negative )
  - Relative mass ( no mass / small / large )
  - Penetrating Power ( low / moderate / high )
  - Relative speed ( slow / fast / very fast )
- 4) For each sentence, state whether it is true or false
  - All nuclear radiation is deflected by magnetic fields
  - Gamma radiation has no mass because it is an EM wave
  - Alpha is the slowest and most strongly ionising type of radiation
  - Beta particles are electrons, so they do not come from the nucleus
- 5) Radiation from three sources - A, B & C - was directed through an electric field towards target sheets of paper, aluminium and lead. Counters were used to detect where radiation passed through the target sheets.
  - Source A - the radiation was deflected by the electric field and stopped by the aluminium
  - Source B - the radiation was partially absorbed by the lead
  - Source C - the radiation was deflected by the electric field and stopped by the paper
    - What type of radiation is emitted by:
      - Source A =
      - Source B =
      - Source C =
    - Why is radiation from source B not deflected by the electric field?
    - What other type of field would deflect radiation from sources A and C?

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Three Types of Radioactivity

There are three types of radiation - alpha (α), beta (β) and gamma (γ).

What are alpha, beta and gamma radiation made from? [3]

Which material can block each type of radiation? [3]

A nucleus decays and emits radiation to become more stable - but what makes some nuclei unstable (and hence radioactive) to begin with? [3]

Classwork

Homework