(d) $(r_{m})\ = \ \left( \frac{m^{2}}{z} \right)(0.53\mathring{\mathrm{A}}) = (n \times \ 0.3)\mathring{\mathrm{A}}$
$\therefore\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \frac{m^{2}}{z} = n$
$m$=5 for $_{100}$Fm$^{257}$ (the outermost shell) and $z = 100$
$\therefore\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ n = \frac{(5)^{2}}{100} = \frac{1}{4}$