Noble gas noble gases show extremely low chemical reactivity; consequently, only a few hundred noble gas compounds have been formed. Neutral compounds in which helium and neon are involved in chemical bonds have not been formed (although there is some theoretical evidence for a few helium compounds), while xenon, krypton, and argon have shown only minor reactivity. The reactivity follows the order Ne < He < Ar < Kr < Xe < Rn. In 1933, Linus Pauling predicted that the heavier noble gases could form compounds with fluorine and oxygen. He predicted the existence of krypton hexafluoride () and xenon hexafluoride (),
Atmosphere of Venus gases, most notably sulfur dioxide. The amount of nitrogen in the atmosphere is relatively small compared to the amount of carbon dioxide, but because the atmosphere is so much thicker than that on Earth, its total nitrogen content is roughly four times higher than Earth's, even though on Earth nitrogen makes up about 78% of the atmosphere. The atmosphere contains a range of compounds in small quantities, including some based on hydrogen, such as hydrogen chloride (HCl) and hydrogen fluoride (HF). There is carbon monoxide, water vapour and atomic oxygen as well. Hydrogen is in relatively short supply in the