Galvanic vs. Electrolytic Cells

Electrons always go from the anode to the cathode. ALWAYS, no matter what kind of cell you have. This is because the cathode is defined as the reducing electrode, while the anode is being oxidized. Again, this is always the case, regardless of what kind of cell it is. What changes for galvanic vs. electrolytic cells is the SIGN of the electrodes. In a spontaneous (galvanic) cell, the negative electrons go from a negatively charged anode down their electrical gradient to a positively charged cathode. Makes sense, right? Negative charges would like to go to a positively charged electrode, given their druthers. On the other hand, in an electrolytic cell, you are forcing the negative electrons to go backward, against their electrical gradient, to a negative electrode. Thus, in electrolytic cells, the anode is now positive while the cathode is negative.

As for what flows to the anode, that would be the current. Recall that current is defined by physicists as the direction that imaginary positive charges would travel (though of course it is the electrons we are concerned with in chemistry, not the current). It is also possible if you were reading about a galvanic cell that the problem might mention ions from the salt bridge moving to the cathode and anode. (Since the electrodes are in separate cells for a galvanic cell, you need the salt bridge to complete the circuit or you won’t get any electron flow.) What happens? Well, when the electrons move from the anode, they leave behind positive charges. So negative charges from the salt bridge (anions) travel to the anode cell to counterbalance them. Conversely, the electrons going to the cathode side would build up a net negative charge if positive ions (cations) from the salt bridge didn’t travel to the cathode side to balance them. So salt bridge anions go to the anode side, and cations go to the cathode side.