Chemistry AS EL CI 2.2

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  • Created by: A.B.
  • Created on: 22-10-13 20:04
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  • EL Nuclear Reactions CI 2.2 SL EL1 EL3
    • Radioactive Isotopes
      • Some isotopes have unstable nuclei
        • Results in isotope being radioactive
      • Emission
        • Capable of knocking electrons out of atoms
          • Referred to as ionising radiation
        • Produced spontaneously by radioactive nuclei
        • Types
          • alpha
            •  
            • Helium nuclei
              •  
            • Relative charge of 2+
            • Lose 2 protons and 2 neutrons from nucleus
            • Stopped by paper (or skin)
            • Low deflection due to mass
          • beta
            •  
            • electron
              •  
            • Relative charge or 1-
            • Gain one proton lose one neutron from nucleus.
              • 1 neutron is converted into a proton and an electron which is ejected from the nucleus.
            • Stopped by aluminium foil
            • High deflection in electric field
          • gamma
            •  
            • Electromagnetic radiation
            • Charge of 0
            • No change in nucleus
            • Stopped by lead sheet
            • No deflection in electric field
      • Dangerous and can cause cancer
    • Equations for radioactive decay
      • With alpha and beta radiation, the atomic number changes and a new element is formed.
        • Look up the symbol in the periodic table
    • Half-life
      • Time taken for half the nuclei in a sample to decay
        • Fixed for any given radioisotope
        • Not affected by temperature
      • Can be used to date archaeological artefacts made from living things.
    • Tracers
      • Radioactive isotopes whose decay is monitered
      • Can be used in medicine to aid diagnosis
      • Tracers are relatively safe - small doses limit exposure and benefits outweigh risks.
    • Nuclear Fusion
      • Joining of 2 or more nuclei to form a heavier nucleus of a new element.
      • High temperatures and pressures
        • Provide energy needed to overcome repulsion
      • Occurs during star formation

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