Element Crossword- Guess the Element

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Across
  1. 2. Number - 7
  2. 5. subatomic - 21
  3. 6. as a refrigerant
  4. 7. up 78% of air
  5. 8. the element - Daniel Rutherford
Down
  1. 1. and odorless appearance
  2. 2. Mass - 14.007
  3. 3. of discovery - 1772
  4. 4. at room temperature
  5. 5. food in gas form