The Periodic Table of Elements

12345678910111213141516
Across
  1. 3. a radioactive element
  2. 5. number 14
  3. 7. chief agents in chemical bonds
  4. 8. first element
  5. 12. has units of atomic mass units
  6. 13. positively charged particle
  7. 15. a gas we breathe
Down
  1. 1. number 15
  2. 2. not solid
  3. 4. gases that do not interact with other atoms
  4. 6. all the matter we know is formed from
  5. 9. the least dense form of matter
  6. 10. neutral particle
  7. 11. symbol Fe
  8. 14. matter that keeps its shape
  9. 16. symbol Au