Across
- 1. is used in balloons and deep-sea diving
- 3. is used as a water purifier for a pool
- 5. is named after a greek word meaning "hidden"
- 9. this element is used in spacecraft.
- 11. the number of protons in a atom
- 12. lose electrons easily
- 13. vertical columns of elements
- 14. horizontal row of elements
- 16. mass of the mixture of isotopes.
- 18. the area around the nucleus in an atom
- 19. same element, different numbers of neutrons
Down
- 2. Particles with electric charge
- 4. is an element of matter
- 6. particles without electric charge
- 7. center of an atom
- 8. arrangement of elements
- 10. comes from a latin word meaning "coal"
- 12. the number of protons and neutrons
- 15. group of six elements
- 17. smaller particles