This is a video tutorial in the Education category where you are going to learn how to describe chemical formulas. A chemical formula represents the actual number of atoms of each element within a molecule. Different visual representations of molecules include the ball and stick three dimensional model, a line drawing that represents the structure in two dimensional terms, and a shorthand used by organic chemists. If a molecule has 4 green atoms and 2 orange atoms, the ratio of green to orange is 2:1. But we cannot write the ratio. Because, there may be another molecule with 2 green atoms and 1 orange atom. And both the molecule will have different physical and chemical properties. Watch the video for the demonstration.