  We present theoretical predictions for electron scattering on oxygen and
calcium isotopic chains. The calculations are done within the framework of the
distorted-wave Born approximation and the proton and neutron density
distributions are evaluated adopting a relativistic Dirac-Hartree model. We
present results for the elastic and quasi-elastic cross sections and for the
parity-violating asymmetry. As a first step, the results of the models are
tested in comparison with some of the data available for elastic and
quasi-elastic scattering on 16O and 40Ca nuclei. Then, the evolution of some
nuclear properties is investigated as a function of the neutron number. We also
present a comparison with the parity-violating asymmetry parameter obtained by
the PREX Collaboration on 208Pb and give a prediction for the future experiment
CREX on 48Ca.
