How difficult is it for electrons to flow through a material?

Electrons 'jump' from one atom to another. The electron configuration of the atoms determine how easy it is for an electron to move from one atom to another, which is a factor in determining conductivity of the substance.

Actually in atoms in the solid state, electrons occupy one of 2 quantum energy bands: the valence band or the conduction band. Valence band electrons are tightly bound to the atom, but conduction band electrons are not bound to the atom and can roam freely through the material.

• insulators have very few if any conduction band electrons and thus cannot conduct
• conductors have so many conduction band electrons that they form what is called an electron gas that fills all of the material and can flow freely, there is no"'jumping' from one atom to another" at all