Liquefaction of gases low temperatures, using, for example, turboexpanders. The liquefaction of air is used to obtain nitrogen, oxygen, and argon and other atmospheric noble gases by separating the air components by fractional distillation in a cryogenic air separation unit. Air is liquefied by the Linde process, in which air is alternately compressed, cooled, and expanded, each expansion results in a considerable reduction in temperature. With the lower temperature the molecules move more slowly and occupy less space, so the air changes phase to become liquid. Air can also be liquefied by Claude's process in which the gas is allowed to expand isentropically
Noble gas noble gases. As a result of a full shell, the noble gases can be used in conjunction with the electron configuration notation to form the "noble gas notation". To do this, the nearest noble gas that precedes the element in question is written first, and then the electron configuration is continued from that point forward. For example, the electron notation of phosphorus is 1s 2s 2p 3s 3p, while the noble gas notation is [Ne] 3s 3p. This more compact notation makes it easier to identify elements, and is shorter than writing out the full notation of atomic orbitals. The