Chemistry

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Across
  1. 5. The particles in the nucleus
  2. 6. The minimum size needed for a chain reaction
  3. 10. holds together protons and neutrons
  4. 14. fusion caused by high temperatures
  5. 16. Building blocks of the universe
  6. 18. The average mass of all the isotopes of an element
  7. 19. In the smallest possible units
  8. 20. Neutral particles in an atom
Down
  1. 1. Electromagnetic radiation from radioactive nuclei
  2. 2. The time it takes for half a sample to decay
  3. 3. The nucleus of a helium atom
  4. 4. Small, negative particles in an atom
  5. 7. When an element decays into another element
  6. 8. Positively charged particles of an atom
  7. 9. When a reaction causes another reaction
  8. 11. The splitting of two nuclei into smaller halves
  9. 12. An electron ejected from a radioactive nucleus
  10. 13. Number of protons and neutrons in an isotope
  11. 15. Amount of protons in an element
  12. 17. The same element with a different number of neutrons