Noble gas Noble gas The noble gases (historically also the inert gases; sometimes referred to as aerogens) make up a group of chemical elements with similar properties; under standard conditions, they are all odorless, colorless, monatomic gases with very low chemical reactivity. The six noble gases that occur naturally are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and the radioactive radon (Rn). These elements are all nonmetals. Oganesson (Og) is variously predicted to be a noble gas as well or to break the trend due to relativistic effects; its chemistry has not yet been investigated. For the first six
Atmosphere of Triton from NASA. Atmosphere of Triton The atmosphere of Triton is the layer of gases surrounding Triton. The surface pressure is only 14 microbars (0.014 hPa or 1 mmHg), of the surface pressure on Earth, and it is composed of nitrogen, similar to those of Titan and Earth. It extends 800 kilometers above its surface. Recent observations have shown an increase in temperature. Nitrogen is the main gas in Triton's atmosphere. The two other known components are methane and carbon monoxide, whose abundances are a few hundredths of a percent of that of the nitrogen. Carbon monoxide, which was discovered only