High Quality Content by WIKIPEDIA articles! The van der Waals radius, rw, of an atom is the radius of an imaginary hard sphere which can be used to model the atom for many purposes. It is named after Johannes Diderik van der Waals, winner of the 1910 Nobel Prize in Physics, as he was the first to recognise that atoms had a finite size (i.e., that atoms were not simply points) and to demonstrate the physical consequences of their size through the van der Waals equation of state.