Radioactivity

Radioactivity

1. Key Definition

   • Half-Life
     • Either:
       • The time taken for the activity to halve.
       • The time taken for the number of undecayed nuclei to halve.
   • Activity
     • The number of decays per second.
   • Isotope
     • An atom of an element with the same number of protons but a different number of neutrons.
   • Radioisotope
     • An unstable isotope that will undergo radioactive decay in order to become more stable.
   • Radioactive Decay
     • The act of spontaneous and random release of radiation.
   • Ion
     • An atom with a charge.
     • Ionisation
       • The act of causing an atom to become an ion.

2. Radiation

   • Background Radiation
     • Some materials give off radiation naturally.
       • For example: Rocks, Air and Space.
   • There are three types of radiation.
     • Alpha
     • Beta
     • Gamma
       • They are stopped by different materials.
     • Radiation Flashcards.
       • Radioactivity

3. Atomic Structure

   • Previously, people believed that the atom looked like a 'plum pudding'.
   • Rutherford Scattering Experiment
     • Ernest Rutherford, a British scientist, proved that the atom had a positive nucleus with negative electrons orbiting it.
     • Alpha particles were fired at thin gold foil.
       • Most particles went through, whilst some were deflected and the rest were reflected.
         • As most past through easily, the atom is mainly empty space.
         • A few were deflected, so...
         • Some were reflected, so...
           • The nucleus is small compared to the rest of the atom, yet it contains most of the mass and of the positive charges.

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