As the nucleus becomes smaller (w.r.t. the electron cloud), the quadrupole magnitude as well decreases (clearest change in the peak and tails of the gausian distribution in classical description of nuclei energy level as a function of its orientation w.r.t. electron cloud – the E2 value drops until it “overlaps” the exact solution as the l/d ratio decreases). In summary the quadrupole term can be seen as the part that adds the rotational dependency in nucleus energy levels.