Physics: section 7 - radioactivity and particles

Physics: section 7 - radioactivity and particles

1. Radioactivity

   • At the centre of every atom is a nucleus
     • The nucleus contains protons and neutrons
     • Electrons are negatively charged
     • The number of protons in the nucleus is called the atomic number
     • The total number of protons and electrons in the nucleus is called the mass number
   • Isotopes are Atoms with different numbers of neutrons
     • Most elements have a range of isotopes
     • Isotopes have the same number of protons, but a different number of neutrons
     • Each element only has 1 or 2 stable isotopes, all the others tend to be unstable and therefore can be radioactive as it decays
   • Radioactive decay is random
     • The nuclei of unstable isotopes break down at random
     • Each nucleus decays spontaneously, it completely unaffected by physical conditions such as temperature
     • When the nucleus decays it spits out one or more types of radiation: Alpha, Beta and Gamma
     • In this process, the nucleus often changes into a new element
   • Background radiation is everywhere all the time
     • Some radioactivity comes from the air, food, building materials, soil rocks . . .
     • Comes from radiation from space (cosmic rays) which are mostly from the sun
     • Some from all living things
     • Human activity such as nuclear explosions contribute to the total

2. The three kinds of radioactivity

3. Alpha scattering and nuclear equations

4. Half-life

5. Uses of nuclear radiatiion

6. Risks from nuclear radiation

7. Nuclear fission

8. Revision questions for section 7

   • 1. List the 3 particles which make up an atom
   • 2. What is the isotonic number of a nucleus ?
   • 3. What is the mass number of a nucleus ?
   • 4. What are isotopes of an element ?
   • 5. Where does background radiation come from ?
   • 6. Give 2 ways you can detect ionising radiation
   • 7. Describe what Alpha, Beta and Gamma radiation are
   • 8. Which is the most ionising type of radiation ?
   • 9. What type of radiation is stopped by paper ?
   • 10. What is the half life of an element ?
   • 11. Describe 3 uses of nuclear radiaition
   • 12. Why is radiation dangerous to living organisms ?
   • 13. Why is radioactive decay hard to get rid of ?
   • 14. What are the products of the nuclear fission of Uranium-235 ?
   • 15. Describe how a chain reaction is set up in a nuclear reactor ?
   • 16. What job do control rods and moderators do in a nuclear reactor ?