The atomicity of a molecule refers to the total number of atoms present in that molecule.

Here's how to determine the atomicity of water (H₂O):

* Hydrogen (H): There are two hydrogen atoms (represented by the subscript "2").

* Oxygen (O): There is one oxygen atom.

Therefore, the total number of atoms in a water molecule is 2 + 1 = 3.

So, the atomicity of water is 3.