Periodic Table and Elements

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Across
  1. 2. Period number of hydrogen and helium
  2. 3. What happens to reactivity as you go down group 7?
  3. 6. Who arranged elements in octaves?
  4. 8. Atoms were arranged by atomic ______ in early periodic tables
  5. 10. Who left gaps in the periodic table
  6. 11. What does a more reactive halogen do to a less reactive halogen in a compound?
  7. 15. Which atomic model was designed by JJ Thompson
  8. 18. Which subatomic particle was discovered leading to the plum pudding model being designed?
  9. 20. Noble gases are _____ because they have full outer shells.
  10. 21. What did James Chadwick discover?
Down
  1. 1. What happens to reactivity as you go down group 1?
  2. 4. Early periodic tables left _____ for undiscovered elements
  3. 5. Which elements form negative ions.
  4. 7. Niels Bohr discovered electron _____.
  5. 9. Rows in the periodic table
  6. 12. What happens to the boiling point of elements as you go down group 0?
  7. 13. Who discovered the nucleus
  8. 14. Which type of radiation proved the existence of the nucleus?
  9. 16. The alpha particle experiments proved the nucleus was ___, dense and in the middle
  10. 17. Columns in the periodic table
  11. 19. Which elements form positive ions?