Here's how to determine the number of valence electrons in ethanol (C2H5OH):

1. Identify the atoms and their valence electrons:

* Carbon (C): 4 valence electrons

* Hydrogen (H): 1 valence electron

* Oxygen (O): 6 valence electrons

2. Calculate the total valence electrons:

* 2 Carbon atoms * 4 valence electrons/atom = 8 valence electrons

* 6 Hydrogen atoms * 1 valence electron/atom = 6 valence electrons

* 1 Oxygen atom * 6 valence electrons/atom = 6 valence electrons

3. Add the valence electrons from all the atoms:

* 8 + 6 + 6 = 20 valence electrons

Therefore, ethanol (C2H5OH) has 20 valence electrons.