P-orbitals form in sets of 6 producing an octahedral structure. By producing this form based on the average radii for each set, we can approximate the radius for almost all elements on the periodic table.
S-orbitals form the only set of elements occupying a spherical shell. Whilst quantum theory suggests it is ‘only applicable’ to these types of atom, investigation of the atomic radius shows a discrepancy of over 100% for some elements.