Physical Science Crossword puzzle

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Across
  1. 2. substance that cannot be broken down
  2. 5. a table in which elements are arranged
  3. 10. number of protons in an atom
  4. 12. good conductor of heat and electricity
  5. 13. smaller than a atom
  6. 14. a particle with no charge
Down
  1. 1. atoms of the same element with different amounts of nuetrons
  2. 3. smallest element particle
  3. 4. the outermost energy level
  4. 5. a positive charged particle
  5. 6. negatively charged particle
  6. 7. inert element in group 18
  7. 8. the sum of protons and nuetrons
  8. 9. middle of an atom
  9. 11. space taken up