The atmosphere of the earth is made up of gases which reside in layers of gas that surround the planet. In order to understand the gases of the atmosphere, it helps to know how the atmosphere is constructed and what goes on in the layers. There are five levels of the atmosphere: the Troposphere, where life forms; the Stratosphere which contains the Ozone Layer; the Mesosphere with a few molecules; the Thermosphere with fewer molecules and large temperature fluctuations; and the Exosphere with few molecules that often escape into space. Between each layer are boundaries with the suffix “pause”. Hence, we have the Tropopause, Stratopause, Mesopause and Thermopause.
With the richest concentration of molecues, the Troposphere is comprised of 80 percent of the atmospheric mass and therefore 80 percent of the gases.
There are other layers, where unique events go on. The Ozone Layer resides in the lower Stratosphere and contains 90 percent of our ozone. At 2 to 8 parts per million, this is the highest concentration of ozone of all of the layers. There are geographical and seasonal fluctuations in the Ozone layer.
There is ionized radiation: The Ionosphere has the most ionized radiation and forms the inner edge of the magnetosphere, while overlapping the exosphere and thermosphere. The most famous effect on the gaseous molecules are the auroras.
In the Homosphere, the gases are mixed by turbulence. The homosphere includes the troposphere, stratosphere and mesosphere. Molecues are so busy being moved around that they are not accounted for by molecular weight.
In the Heterosphere, there is less turbulence and the gases layer out according to there molecular weight. Oxygen and nitrogen are at the bottom of the Heterosphere, with hydrogen, the lightest element, at the top. The Heterosphere is above the turbopause.
The Planetary Boundary Layer is closest to the Earth’s surface and can vary from 100m to 3000m, depending on moisture, calmness, and clarity of the air at night.
Of the entire atmosphere, the gases are Nitrogen (78%), Oxygen (20.9%), Argon (.93%), Carbon Dioxide(.039%), Neon, Helium, Methane, Krypton, Hydrogen, Nitrous Oxide, Xenon, Ozone, Nitrogen Dioxide, Iodine, Carbon Monoxide, Ammonia and in some cases, water vapor (h20).
Helium, Krypton, Argon and Neon are the noble gases (you can see the noble gases properties), which have extremely low levels of reactivity with other elements. They are also referred to as inert gases. Imagine extracting these from the air!
http://en.wikipedia.org/wiki/Atmosphere_of_Earth
http://www.eoearth.org/article/Atmospheric_composition_and_structure
