Five atoms
It depends on how many hydrogens are there and how many oxygen atoms there are.
2 atoms
4 atoms are in h202.
Divide that number of atoms by 6.02x10^23 atoms/mole
There many, many structures with that formula. I just did a quick search for chemicals with that formula available from Sigma-Aldrich and several other vendors, and came up with 15 hits; I'm sure there are more. The only one of the 15 whose name I immediately recognized is aflatoxin P2. Some others: kaempferide, hematein, acetylsalicylacetylsalicylate (I recognize what this IS, but not what it's used for), chrysoeriol, orientin, geraldol, piperoin, hispidulin, diosmetin... any of those ring a bell for you?
10
There are 20 atoms and there are 6 Carbon atoms, 8 Hydrogen atoms, 6 Oxygen atoms.
C8H16O8 has a total of 24 atoms (8 carbon atoms, 16 hydrogen atoms, and 8 oxygen atoms).
5 atoms
9 atoms
45 atoms
Five atoms
402 atoms
There are 12 atoms in one mole of magnesium (Mg), which is equivalent to 6.022 x 10^23 atoms.
To answer your question on how many hydrogen atoms are there in caffeine, the scientific answer would be 10 atoms of hydrogen.
Answer: 8 atoms