Across
- 2. natural state is gas.
- 4. is a yellow-greenish gas.
- 6. has 6 valence electrons
- 9. has 5 neutrons.
- 11. is highly reactive.
- 12. scientific name is Ferrum.
- 13. was known by the Greek and the Romans in 20 b.c.
- 15. was discovered in 3500 b.c. in ancient Egypt.
- 17. was discovered in 2000 b.c.
- 18. is the name after the U.S. five cent.
- 19. has 12 valence electrons.
- 20. is the 4th most abundant.
Down
- 1. has an atomic mass of 11.
- 3. was discovered twice.
- 5. comes from Germany.
- 6. is everywhere even your device.
- 7. has the lowest melting point of all elements.
- 8. can suffocate in high density.
- 10. is not reactive to oxygen.
- 14. has 19 protons.
- 16. is from Scandinavia.