Maxton's atom vocabulary word puzzle

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Across
  1. 4. has an atomic number and can't be broken down
  2. 6. the symbol for diatomic hydrogen
  3. 9. made up of two or more elements
  4. 10. part of a nucleus with no electric charge
  5. 13. the middle of an atom
  6. 14. in H2O the 2 is a
  7. 15. reactants turn into this during a reaction
  8. 17. a negatively charged part of an atom
Down
  1. 1. abbreviations for chemical elements
  2. 2. enables the formation of molecules
  3. 3. electrons can be free or
  4. 5. the symbol for oxygen
  5. 6. the symbol for water
  6. 7. a table showing the chemical elements
  7. 8. a group of atoms
  8. 11. part of a nucleus with a positive electric charge
  9. 12. the basic building block of chemistry
  10. 16. something that changes during a reaction