 The polarizability is related the van der Waals volume by the relation
so the van der Waals volume of helium "V" =  = 0.2073 Å by this method, corresponding to "r" = 0.37 Å.When the atomic polarizability is quoted in units of volume such as Å, as is often the case, it is equal to the van der Waals volume.However, the term "atomic polarizability" is preferred as polarizability is a precisely defined (and measurable) physical quantity, whereas "van der Waals volume" can have any number of definitions depending on the method of measurement.