Atmospheric Composition
Gas Name Chemical Formula Percent Volume
Nitrogen N_2 78.08%
Oxygen O_2 20.95%
*Water H_2O 0 to 4%
Argon Ar 0.93%
*Carbon Dioxide CO_2 0.0360%
Neon Ne 0.0018%
Helium He 0.0005%
*Methane CH_4 0.00017%
Hydrogen H_2 0.00005%
*Nitrous Oxide N_2O 0.00003%
*Ozone O_3 0.000004%
Notes
- The table shows the composition by volume averaged over lower 25 km
of the atmosphere.
- Gases which are variable are marked by asterisks.
- Recall the ideal gas law PV=NkT, where P is pressure, V is Volume,
N is particle density, k is Boltzmann's constant, and T is
Kelvin Temperature.
Insofar as the ideal gas law is valid and P and T can be regarded as mean values,
then for each component i we have P_iV=N_ikT. Thus,
V_i/V=N_i/N. Thus the composition by volume is roughly the composition by
number fraction.
-
Michael J. Pidwirny Fundamentals of Physical Geography.