Atomic theory crossword puzzle

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Across
  1. 2. any particle that is smaller than an atom
  2. 3. subatomic particle with a positive charge
  3. 5. a basic unit in which all matter is made
  4. 7. has no electrical charge
  5. 9. the number of protons an oxygen atom has
Down
  1. 1. the number of protons in the nucleus of an atom
  2. 4. the charge of an electron
  3. 6. the charge of a proton
  4. 7. the center of an atom
  5. 8. a subatomic particle with a negative electrical charge