How many electrons will be transferred between a sodium and gallium electrode from the following? So here we have gallium ion absorbing 3 electrons to become gallium solid. Gallium goes from +3 to 0 so it's oxidation number was reduced so it represents the catheter. Remember we know that this is the cathode because the catheters were a reduction occurs. Also, we know that this is a reduction because the electrons are reactants.
Sodium on the other hand goes from a neutral charge to +1. Its oxidation number increased, so it's been oxidized, which means it's the anode. We also know it's an oxidation because your electrons are products. Now remember your electrons are intermediates and they have to cancel out with each other. Here they can't because one says 3 electrons and one says only one.
You would multiply this equation by three so that both half reactions have the same number of electrons. Doing that tells me that three electrons are transferred between the sodium and gallium electrodes. 3 electrons are lost by the anode half cell and given over to the cathode half cell, right? So 3 electrons will be transferred within this particular example question.