Only in straight uniform motion of a charge does its electric field point to its instantaneous position obeying actio et reactio. Accelerated charges exchange energy and momentum with the electromagnetic field while the sum of energies and the sums of the spatial momenta remain conserved. By Noether’s Theorems these conservation laws correspond to the invariance under translations in spacetime. The electrodynamic interactions (not the masses of the charged particles) are also invariant under dilations. This is why these interactions alone cannot explain the particular values of particle masses or the particular sizes of atoms.