crossword puzzle

1234567891011121314151617181920
Across
  1. 4. a chemical element with the symbol Na and atomic number 11.
  2. 7. a chemical element with the symbol Sr and atomic number 38.
  3. 9. a chemical element with the symbol Xe and atomic number 54.
  4. 11. a chemical element with the symbol N and atomic number 7.
  5. 12. a chemical element with the symbol Ca and atomic number 20.
  6. 15. a chemical element with the symbol S and atomic number 16.
  7. 16. a chemical element with the symbol I and atomic number 53.
  8. 18. a transuranic radioactive chemical element with the symbol Cm and atomic number 96.
  9. 20. a chemical element with the symbol Rn and atomic number 86.
Down
  1. 1. a chemical element with the symbol Hf and atomic number 72.
  2. 2. a chemical element with the symbol Cl and atomic number 17.
  3. 3. a chemical element with the symbol Si and atomic number 14.
  4. 5. a synthetic chemical element with the symbol Ts and atomic number 117.
  5. 6. a chemical element with the symbol Au and atomic number 79.
  6. 8. a chemical element with the symbol U and atomic number 92.
  7. 10. a chemical element with the symbol Bi and atomic number 83.
  8. 13. a chemical element with the symbol Li and atomic number 3.
  9. 14. a chemical element with the symbol B and atomic number 5.
  10. 17. a chemical element with the symbol Pb and atomic number 82.
  11. 19. a chemical element with symbol Fe and atomic number 26.