Radioactivity

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Across
  1. 1. years taken for activity to go from 1200Bq to 75Bq if half life is 2 years
  2. 4. electromagnetic radiation from the nucleus
  3. 5. particle used to cause fission of U-235
  4. 6. type of radiation that is always present
  5. 11. number of half lives for activity to fall from 24 to 6
  6. 12. made of two protons and two neutrons
  7. 13. natural fusion reactor
  8. 14. the atom is mostly _______ space
  9. 16. half life in second if activity drops from 240 to 30Bq in 9 seconds
  10. 18. atoms with different mass numbers
  11. 22. high density metal needed to stop gamma
  12. 23. responsible for plum pudding model of the atom
Down
  1. 2. a source used to follow a process in the body or elsewhere
  2. 3. nuclei coming together
  3. 5. charge of gamma ray
  4. 7. metal that stops beta but not gamma
  5. 8. his model was supported by the alpha scattering experiment
  6. 9. an electron emitted from the nucleus
  7. 10. charge of beta particle
  8. 15. charge of alpha particle
  9. 17. radioactive gas
  10. 19. substance that will stop alpha but not beta
  11. 20. radiation from space
  12. 21. type of foil used in rutherfords scattering experiment