Periodic table

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Across
  1. 6. highly reactive metal group
  2. 7. 2 elements chemically combined
  3. 8. carbon dioxide
  4. 11. visual representation of a atom
  5. 13. O
  6. 14. water
  7. 15. positive charge
  8. 19. pure substance on its own
  9. 20. negative charge
Down
  1. 1. visual representation of valence electrons in atom
  2. 2. sum of protons and nuetrons
  3. 3. Rows on periodic table
  4. 4. atoms on outer ring
  5. 5. where do you find elements?
  6. 9. C
  7. 10. group 18 on periodic table
  8. 12. group 17
  9. 16. slt
  10. 17. protons in nucleous
  11. 18. Collums on periodic table