Radioactivity

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Radioactivity

• Chapter 8

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Radioactivity

• Radioactivity is the emission of alpha, beta or
  gamma radiation from the nucleus of unstable
  atoms.
• It was discovered by Becquerel, who found that an
  uranium salt had affected a photographic plate.
  Pierre and Mari Curie found two new radioactive
  elements- polonium and radium.
• .

Becquerel,
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Pierre and Marie Curie

• For their work on radioactivity, the Curies were
  awarded the 1903 Nobel Prize in physics. A year
  later, Marie was awarded the Nobel Prize in
  chemistry for her discoveries of radium and
  polonium, thus becoming the first person to
  receive two Nobel Prizes.

Marie Curie ca. 1920. Inset Pierre Curie
(Marie's favorite picture of her husband).
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Geiger-Muller Tube

• Radioactive radiation can be detected using a
  Geiger Muller tube

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Alpha radiation

• Alpha radiation consists of a stream of
  positively charged particles and so are deflected
  towards the negatively charged plate, and by a
  magnetic field.
• Alpha particles consists of two protons and two
  neutrons which is the same as the nucleus of
  Helium.
• The have low penetrating power and are stopped by
  a few centimeters of Air or a sheet of paper.
• Examples of elements which emit alpha particles
  is americium-241(smoke detectors).

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Beta Particles

• Beta particles are simply electrons. A beta
  particle is formed when a neutron is changed into
  a proton and an electron.
• They are more penetrating than Alpha particles
  and can penetrate up to 5mm of aluminium.

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Gamma radiation

• Gamma radiation is high energy electromagnetic
  radiation of very short wavelength. It is not
  deflected in electric or magnetic fields. Gamma
  rays have high penetrating ability.
• Cobalt-60 gives off Gamma radiation. Used to kill
  cancerous cells.

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Differences
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Half Life

• The Half-life of an element is the time taken for
  half of the nuclei in any given sample of decay.

http//www.darvill.clara.net/nucrad/types.htm
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Uses of Radio-isotopes

• Medicine- Cobalt-60 kill cancer cells
• Food preservation Gamma rays kill microbes
• Industry- Tracers added to find source of
  leaking pipes
• Archeology- Carbon-14 dating by beta
  emmission

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Radon