Periodic table

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Across
  1. 3. Metal with variable valency 1 and 2
  2. 6. Noble gas with a duplet
  3. 8. A neutral gas
  4. 9. Supporter of combustion
  5. 10. Gives a brick red flame
Down
  1. 1. Radioactive elements
  2. 2. A highly reactive metal
  3. 3. A monovalent nonmetal
  4. 4. Valency of Group 18 elements
  5. 5. A metalloid in Period 3
  6. 7. Electrons in the outermost orbit