How many familiar two-word phrases can you think of in which the first word is an element? 

Example: GOLD STANDARD

(Possible) Answers:

1. Silver spoon/lining

2. Tin ear

3. Iron will/fist

4. Carbon copy/dating/footprint

5. Helium balloon

6. Hydrogen bomb

7. Lithium battery

8. Oxygen tank

9. Aluminum siding

10. Silicon Valley

11. Neon sign 

12. Copper wire

13. Lead weight/balloon

14. Barium enema 

15. Sodium pentothal