"CO"_2 has one carbon atom and two oxygen atoms, so it is called carbon dioxide. It's a gas you can find anywhere on Earth that has air, and it's why the pH of everyday water open to the air is less than 7 (it dissolves in water to make some "H"_2"CO"_3, an acid in soda).
:stackrel(..)"O"="C"=stackrel(..)"O":
"C"_6"H"_12"O"_6 corresponds to many different compounds, but I presume you mean glucose (a six-carbon sugar), which plants make from photosynthesis. It's also made and/or utilized in our bodies, in for example, the citric acid cycle, glycolysis, etc.
The following structure has the name alpha-D-glucopyranose:
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It does break open in water, but it exists primarily (99%) as this ringed structure in water.
"ATP", or adenosine triphosphate, is often referred to as the energy carrier in the cells of many organisms. It holds three phosphate groups, and essentially releases and re-binds to one or two phosphate groups to transport energy.
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