Half-life of Radioactive materials & nature of nuclear radiatiors

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  • Created by: Katy **
  • Created on: 03-01-14 17:11

Atoms

Nucleus:

  • protons → mass = 1 (+1)
  • neurons → mass = 1 (0)

Orbits:

  • electrons → mass = negligble (-1)
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Radioactive

  • Elements / atoms with an imbalance between the no. protons & no. neutrons.
  • Elements / atoms that have a nuclei larger than Lead = unstable.
  • When they give off radiation they become -

◘ more stable

◘ may change to other elements

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Radioisotopes

Iosotpe of an element has:

  • same no.protons
  • different no. neutrons


  • Radioisotopes are isotopes that are radioactive.
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Measuring Radioactivity

Measurements allow for:

  • randomness of decay - measure over a long time (average)
  • background radiation - measure background radiation & subtract
  • Unit - becquerel (Bq)
  • 1 disintergration per second
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Half-life

Time taken for:

  • activity of sample to reduce to half its initial amount
  • no. sunstable nuclei to reduce to half initial amount
  • Nothing can change the half-life of an isotope (not thermal / chemical / physical)
  • Half-life varies from secondsyears
  • shorter half-life = more unstable
  • more radioactive isotope = shorter life
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Uses of Radioactive material

Domestic:

  • smoke alarms (alpha)stopped by smoke (10yrs half-life)

Archaeology:

  • carbon 14 datingnatural ratio of carbon in living things

Industrial:

  • leaks from gas water pipes (gamma) → to source & check for radiation (days half-life)

Medical:

  • steralising equipment → iteam radiated = destroy bacteria (gamma)
  • cancer treatment → external (gamma) - destroys cancer cells
  • internal (beta & alpha) - to site = control & high ionising
  • (24 hours half-life)
  • tracers → radiation & time to collect & monitor (not alpha as kill patient & high ionising)
  • labelled material(not beta as detected & ionising)
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