According to the free electron model, the valence electrons in a crystalline metal are considered
to be detached from the atoms and able to move throughout the material with infrequent
deflections from their paths. Yet the electrostatic potential due to a lattice of ionized atoms has
strong gradients and ought to deflect electrons easily. Why does an individual electron not see a
potential with strong spatial variation? Briefly discuss why an electron in a crystalline metal is
only rarely deflected by the weakly varying potential it actually does see.