Nitrogen

Nitrogen was chemical element present on a number of planets. Justicia and Triton both were cold planets that had nitrogen in the atmosphere, on Justicia it was rendered as snow when the planet moved away from the warming sun, while Triton had a thin atmosphere compose of hydrogen. (NSA: The Monsters Inside, PDA: The Devil Goblins from Neptune)

The 456 thrived in an atmosphere composed (in addition to other elements) 20 percent nitrogen. (TW: Children of Earth: Day Two)