| Permanent Gases |
Variable Components |
|
|
|
Percent (by Volume) |
|
|
|
Percent |
Parts per |
| Gas |
Symbol |
AMU* |
Dry Air |
Gas or Particles |
Symbol |
AMU |
(by Volume) |
Million (ppm) |
| Nitrogen |
$\mbox{N}_2$ |
28 |
78.08 |
Water Vapor |
$\mbox{H}_{2}\mbox{O}$ |
18 |
0-4 |
0-40,000 |
| Oxygen |
$\mbox{O}_2$ |
32 |
20.95 |
Carbon Dioxide |
$\mbox{CO}_2$ |
44 |
0.0385 |
385 |
| Argon |
Ar |
40 |
0.93 |
Methane |
$\mbox{CH}_4$ |
16 |
0.00017 |
1.7 |
| Neon |
Ne |
10 |
0.0018 |
Nitrous Oxide |
$\mbox{N}_{2}\mbox{O}$ |
44 |
0.00003 |
0.3 |
| Helium |
He |
4 |
0.0005 |
Ozone |
$\mbox{O}_3$ |
48 |
0.000004 |
0.04 |
| Hydrogen |
$\mbox{H}_2$ |
2 |
0.00006 |
Particles |
|
|
0.000001 |
0.01-0.15 |
| Xenon |
Xe |
131 |
0.000009 |
CFCs |
|
|
0.00000002 |
0.0002 |
* - AMU stands for the atomic mass unit of the atom or molecule. It is the sum of the
number of protons and neutrons that comprise the atom or molecule.
The AMU for a sample of the earth's atmosphere is given by the weighted average of the sample's constituent. That is,
AMU (for the sample) = 0.7808 $\times$ 28 + 0.2095 $\times$ 32 + 0.0093 $\times$ 40 $\approx$ 28.9