  We compute the charge radii of even-mass neon and magnesium isotopes from
neutron number N = 8 to the dripline. Our calculations are based on
nucleon-nucleon and three-nucleon potentials from chiral effective field theory
that include delta isobars. These potentials yield an accurate saturation point
and symmetry energy of nuclear matter. We use the coupled-cluster method and
start from an axially symmetric reference state. Binding energies and
two-neutron separation energies largely agree with data and the dripline in
neon is accurate. The computed charge radii have an estimated uncertainty of
about 2-3% and are accurate for many isotopes where data exist. Finer details
such as isotope shifts, however, are not accurately reproduced. Chiral
potentials correctly yield the subshell closure at N = 14 and also a decrease
in charge radii at N = 8 (observed in neon and predicted for magnesium). They
yield a continued increase of charge radii as neutrons are added beyond N = 14
yet underestimate the large increase at N = 20 in magnesium.
