"hard" spelling crossword

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Across
  1. 4. an elementary particle that is identical with the nucleus of the hydrogen atom
  2. 6. relationship
  3. 7. each of more than one hundred substances
  4. 8. always late or never shows up
  5. 12. arrogant
  6. 13. in definite proportions joined by chemical bonds into a molecule
  7. 15. a jealous desirable
Down
  1. 1. self-punishment
  2. 2. a short half-laugh
  3. 3. a person who studies birds
  4. 5. squirming
  5. 7. a very small particle that has a negative charge of electricity and travels around the nucleus of an atom
  6. 9. a particle of matter that uniquely defines a chemical element
  7. 10. quite a harsh laugh/expressing contempt
  8. 11. group of atoms bonded together, representing the smallest fundamental unit of a chemical compound that can take part in a chemical reaction.
  9. 14. a membrane-bound organelle that contains the cell's chromosomes