What does pure air consist of?

Answer 1

Chemical composition of pure dry standard air:

Gas

Volume

Nitrogen (N2)

780,840 ppmv (78.084%)

Oxygen (O2)

209,460 ppmv (20.946%)

Argon (Ar)

9,340 ppmv (0.9340%)

Carbon dioxide(CO2)

394.45 ppmv (0.039445%)

Neon (Ne)

18.18 ppmv (0.001818%)

Helium (He)

5.24 ppmv (0.000524%)

Methane (CH4)

1.79 ppmv (0.000179%)

Krypton (Kr)

1.14 ppmv (0.000114%)

Hydrogen (H2)

0.55 ppmv (0.000055%)

Nitrous oxide(N2O)

0.325 ppmv (0.0000325%)

Carbon monoxide(CO)

0.1 ppmv (0.00001%)

Xenon (Xe)

0.09 ppmv (9×10−6%) (0.000009%)

Ozone (O3)

0.0 to 0.07 ppmv (0 to 7×10−6%)

Nitrogen dioxide (NO2)

0.02 ppmv (2×10−6%) (0.000002%)

Iodine (I2)

0.01 ppmv (1×10−6%) (0.000001%)

Ammonia (NH3)

trace

Not included in above dry atmosphere:

Water vapor(H2O)

~0.40% over full atmosphere, typically 1%-4% at surface