Subheading 280410: Hydrogen
Subheading 280421: Gases, Rare; Argon
Subheading 280429: Gases, Rare; other than Argon
Subheading 280430: Nitrogen
Subheading 280440: Oxygen
Subheading 280450: Boron; Tellurium
Subheading 280461: Silicon; Containing by Weight not Less than 99.99% of Silicon
Subheading 280469: Silicon; Containing by Weight Less than 99.99% of Silicon
Subheading 280470: Phosphorus
Subheading 280480: Arsenic
Subheading 280490: Selenium