Chemistry crossword puzzle

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Across
  1. 7. center of a cell
  2. 8. radioactive
  3. 12. the amount of space that a substance or object occupies
  4. 16. a plot of neutrons
  5. 17. negative
  6. 18. protons+neutrons
  7. 19. electrons treated as waves
  8. 20. high energy
Down
  1. 1. the time it takes for radioactive atoms to decay half way
  2. 2. can release radiation
  3. 3. neutral
  4. 4. positive
  5. 5. a discrete packet of energy or matter
  6. 6. a method to represent a particular isotope
  7. 9. number of protons
  8. 10. to the smallest component of an element
  9. 11. a form of an element
  10. 13. protons(+/-)=electrons
  11. 14. smallest particle
  12. 15. Low and stable