Ball and stick 3D model of the water molecule (H2O) free for download. Molecular structure in this model is scientifically accurate (104.5 degree). The H2O molecule is also known as the water molecule. It is composed of two hydrogen atoms and one oxygen atom. The molecular weight of this compound is 18 g/mol, and it has a molar mass of 18 g/mol. This means that 1 mol H2O contains 60218000 grams (6 × 1023) molecules. The H2O molecule has a linear geometry and a straight line bonding between each of the atoms (on average 137 pm). The interatomic distance in hydrogen is very small (75 pm), and oxygen is relatively big (96 pm). There are two molecules in the centre of this model, and they are bound by strong interactions. Also, they can move themselves freely in all directions following their binding interactions. The most important feature of this 3D model is that it shows clearly lines of symmetry.