Periodic table vocabulary

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Across
  1. 2. everything to the left of the staircase
  2. 4. group 18
  3. 5. sphere in an element
  4. 9. energy levels
  5. 10. number of protons
  6. 12. vertical
  7. 16. metal everything to the right of the staircase
  8. 19. top right and bottom left corners of the periodic table
  9. 20. the origin of every atom.
Down
  1. 1. weight of the nucleus in an atom
  2. 3. group 17
  3. 6. weight of all isotopes of an atom
  4. 7. variety of types of atoms in an element
  5. 8. electrons are not equal to the number of protons in an atom
  6. 11. example
  7. 13. It is mined, or made in a laboratory
  8. 14. weight
  9. 15. everything on the staircase
  10. 17. horizontal
  11. 18. table chart