Atmosphere atmospheres were then modified over time by various complex factors, resulting in quite different outcomes. The atmospheres of the planets Venus and Mars are primarily composed of carbon dioxide, with small quantities of nitrogen, argon, oxygen and traces of other gases. The composition of Earth's atmosphere is largely governed by the by-products of the life that it sustains. Dry air from Earth's atmosphere contains 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and traces of hydrogen, helium, and other "noble" gases (by volume), but generally a variable amount of water vapor is also present, on average about 1% at
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