Bonding and Structure Cryptic(ish) Crossword

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Across
  1. 2. bond, they are mainly all at sea
  2. 4. electrons are these, in our notes
  3. 6. x and y axis, all alone
  4. 8. footballs of carbon
  5. 9. be right back in a degree said the tin
  6. 11. intelligient enough to make a change
  7. 13. say cheese, to get my colour
  8. 14. sharing, we both have in common.
  9. 15. can take a hammering
  10. 16. opposites attract
  11. 18. red hot ice blue
  12. 21. are every 7 days, Alton Towers the London Eye for example
  13. 22. I've lost an e
Down
  1. 1. small and transparent, for use in good weather
  2. 3. polygon plastic with a touch of elephant saying
  3. 5. easy atoms joined, very ready to part company
  4. 7. not from here and negatives, currently sailing
  5. 10. tiny, grans in bits
  6. 12. structure of oppsites that goes on in all directions
  7. 17. tough, you'll shine in the rough
  8. 19. it'll kill you if you are bug small
  9. 20. x and y axis having a scrap, layered