  Charge radii of neutron deficient 40Sc and 41Sc nuclei were determined using
collinear laser spectroscopy. With the new data, the chain of Sc charge radii
extends below the neutron magic number N=20 and shows a pronounced kink,
generally taken as a signature of a shell closure, but one notably absent in
the neighboring Ca, K and Ar isotopic chains. Theoretical models that explain
the trend at N=20 for the Ca isotopes cannot reproduce this puzzling behavior.
