Revision-crossword puzzle

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Across
  1. 2. the smallest particle of a chemical element that can exist
  2. 4. elements with same number of protons but different numbers of neutrons
  3. 7. produce and discharge (a substance)
  4. 8. large white blood cell that ingests foreign particles and infectious microorganisms by phagocytosis
  5. 9. a substance used to provide immunity against one or several diseases
Down
  1. 1. my charge is positive
  2. 2. substance that can release a proton (for example HCl)
  3. 3. the smallest structural and functional unit of an organism, consisting of cytoplasm and a nucleus
  4. 5. mathematical function that describes the wave-like behavior of an electron
  5. 6. lightest element known