Discribe the difference between a material that is a good conductor of electicity and a material that has a hi?

Hi Daisy, in case of good conductors of electricity such as metals the conduction band would just mingled with or get overlapped with the valence band. This overlapping would be greater in case of conductor and very weak in case which has comparatively high resistance. If these two bands are well separated by some energy difference usually called as forbidden gap, then the material becomes an insulator. Very very high resistance.