Molecules in the solar system

The sun, the planets, and everything else in the solar system is made of atoms (or, sometimes, ions, which are atoms that have more or fewer electrons than usual). There are 92 kinds of atoms (or 92 ``elements'') Some of the elements:

1 H hydrogen
2 He helium
...
6 C carbon
7 N nitrogen
8 O oxygen
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12 Mg magnesium
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14 Si silicon
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16 S sulfur
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18 Ar argon
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26 Fe iron
...
92 U uranium
Of these, hydrogen is by far the most abundant element in the solar system and in the universe. The sun is mostly made of hydrogen. (In the sun, it's just hydrogen nuclei and electrons, not hydrogen molecules.) Helium is the second most abundant element. The sun's energy comes from nuclear fusion that turns hydrogen into helium.
In cool places, the atoms can be joined together to make molecules. Here are some examples:

H₂ hydrogen. The hydrogen molecule consists of two hydrogen atoms.
N₂ nitrogen. The main constituent of the earth's atmosphere.
O₂ oxygen. The second most abundant constituent of the earth's atmosphere.
H₂O water. The earth has lots. There is a lot of the frozen kind in the outer parts of the solar system.
NH₃ ammonia. A smelly gas. Makes Neptune blue.
CH₄ methane. An oderless gas. ``Natural gas'' used in gas stoves is mostly methane. (The gas company adds something to it so that you can smell it if it gets out of the pipe without being burned.)
CO₂ carbon dioxide. An oderless gas. Plants use it. Burning material containing carbon (C) makes carbon dioxide.
CaCO₃ calcium carbonate or limestone. An example of a rock.
SiO₂, silicon dioxide or quartz. An example of a rock.

Davison E. Soper, Institute of Theoretical Science, University of Oregon, Eugene OR 97403 USA soper@bovine.uoregon.edu