Across
- 2. - Historically used in pipes
- 3. - Used in party balloons
- 6. - Used in nuclear reactors
- 8. - Used in water purification
- 13. - The lightest element
- 14. - Makes up the majority of Earth's atmosphere
- 15. - Essential for human respiration
Down
- 1. - Precious metal in jewelry
- 4. - Only metal that's liquid at room temperature
- 5. - Used in computer chips
- 7. - Valuable precious metal
- 9. - Noble gas in neon signs
- 10. - Found in steel
- 11. - Reacts explosively with water
- 12. - Basis of organic chemistry