What are the layers of the atmosphere and the gases in each layer? What is the weight of each gas and the height ranges between each layer of gas?

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The Earth's atmosphere consists of a layer of different gases held in place by gravity. The atmosphere protects Earth by absorbing solar radiation, retaining heat, and regulating temperature extremes. The atmosphere has five different levels: the exosphere, the thermosphere, the mesosphere, the stratosphere, and the troposphere. Since there are so many layers and we are limited in space, below are a few ideas to help get you started as well as an equation below to help you calculate for each layer's weight, which is actually called density.

The exosphere is the atmosphere's uppermost layer. The exosphere starts from the exobase, which is the top of the thermosphere, and extends until it merges with outer space. The exosphere starts at 700 km (440 mi) above sea level and extends to about 10,000 km (6,200 mi). The exosphere is also made up of the earth's lightest gases, which are mostly hydrogen, helium, carbon dioxide, and atomic oxygen.

The thermosphere is the second-highest level and extends from the mesosphere to what we call the thermopause, which is where the thermosphere ends. The altitude range of the thermosphere starts at about 80 km (50 mi) to 500-1,000 km (310-620 mi). The gases in the thermosphere, as well as in the troposphere, stratosphere, and mesosphere, consist of atomic oxygen, molecular oxygen, atomic nitrogen, molecular nitrogen, helium, and hydrogen.

If you are looking for the weight of each atmospheric level and the gases within each atmospheric level, you are actually looking for the density, specifically the air density or atmospheric density. One can simplify the equation for calculating atmospheric density by assuming the air is dry, giving only negligible errors in the results. The equation to calculate air density is

` ` `D=P/(R*T)`

` ` where:   D = density, kg/m3 
             P = pressure, Pascals ( multiply mb by 100 to get Pascals)
             R = specific gas constant , J/(kg*degK) = 287.05 for dry air
             T = temperature, deg K = deg C + 273.15

So, if we know the temperature of each level and the air pressure within each level, we can calculate each level's density. We can also use for air pressure the International Standard Atmosphere (ISA) model, which is 101,325 Pascals. We can also use 287.05 as the specific gas constant for dry air. Using the exosphere as our example, the exosphere is understood to be extremely hot, at 2,500 degrees Celsius. So, plugging in our variables, we get


D=(101,325)/287.05*(2,500+273.15)=
              287.05  * 2,773.15  
D=(101,325)/796,032.7075 kg/m3

D=0.1273 kg/m3

Therefore, the weight, or density of the exosphere is 0.1273 kg/m3 and calculations can be continued from there.

To calculate just the density of each layer of gas in each level of atmosphere, the equation is generally the same, density is the weight of the gas divided by the by the standard molar volume is 22.4 L/mol or

`D=(FW)/22.4`

` `where FW represents the formula weight and is in g/mole. To find the formula weight, consult the periodic table of elements to find the grams per mole for the particular gas in question and then divide that by your standard volume.

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