Here's how to determine the number of atoms in a molecule of ethanol (C2H6O):

* Count the subscripts:

* There are 2 carbon atoms (C2)

* There are 6 hydrogen atoms (H6)

* There is 1 oxygen atom (O)

* Add the atoms together: 2 + 6 + 1 = 9

Therefore, there are 9 atoms in a molecule of ethanol.