PS. Chm 1.2

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Across
  1. 3. neutral
  2. 5. decay period
  3. 6. noble gas group
  4. 7. particles
  5. 8. electrons pairs
  6. 9. varies
Down
  1. 1. table elements
  2. 2. negative
  3. 4. group 18
  4. 6. positive