Abundances of elements

solar system* Earth* collection efficiency (percent)

hydrogen 27,000,000,000 9,500 0.00003

helium-4 2,200,000,000 0.00005 0.000000000002

carbon 12,000,000 360 0.003

nitrogen 2,500,000 79 0.003

oxygen 20,000,000 3,400,000 17

neon-20 3,300,000 0.000093 0.000000003

magnesium 1,100,000 1,100,000 100

sulfur 520,000 98,000 19

argon-36 88,000 0.00018 0.0000002

argon-40 0.55 0.053 **

iron 900,000 1,200,000 133

krypton-84 26 0.0000036 0.0000036

*Abundances indicate how many atoms of each element (or, in the case of the noble gases, isotopes) would accompany one million silicon (Si) atoms. For example, the abundance of nitrogen (N) in the solar system is 2.5 times greater than that of Si, whereas its abundance on Earth is less than that of Si by a factor of 0.000079. The table includes the eight most abundant volatile elements, together with others.

**See text.