Introduction, the asymmetry is expected to be measured at $q\approx0.4~fm^{-1}$ [@prex]. Also, because the target is a heavy nucleus ($^{208}$Pb), the above results for the asymmetry should be reconsidered for a detailed comparison with the experiment, since they were obtained using a Plane Wave Born Approximation for the electron [@horo98]. For our present purposes, eq. (\[ass\]) is sufficient to illustrate the sensitivity to the different model parametrizations and is used next in the presentation of our numerical results.

The surface energy per unit area of the droplets in the small surface thickness approximation, excluding the electromagnetic field, reads [@gotas] $$\sigma=\int_0^\infty \d r \left[ \left(\frac{\d \phi}{\d r}\right)^2-
\left(\frac{\d V_0}{\d r}\right)^2 -
\left(\frac{\d b_0}{\d r}\right)^2 \right].
\label{sig}$$ However, as the electromagnetic interaction does not contribute to surface properties directly, we have kept the same definition for the surface energy.

In Table II we show the neutron and proton radius, the neutron skin thickness, the binding energy and the surface energy obtained within the Thomas-Fermi approximation and the two different numerical prescriptions described in the previous sections. All the results are sensitive to the numerical calculation although the analytical approximation is the same. When the nucleation method is performed, the neutron radius is 