 So an electrochemical cell, a simple galvanic cell is a battery and they're made up of two half cells and that's what we're going to focus on drawing today. In order to figure out how to draw the half cells, you need to know some information about the reactivity of the components inside the half cells and also things like solutions, they can help you out as well. You need to be able to figure out which side is going to be the reduction side and which side is going to be the oxidation side. So let's do some example questions. So in this question it says you have a metal activity series here. So we've got calcium being the most reactive, cadmium being the least reactive. It says the diagram represents a cell set up. We've got magnesium and nickel. You need to label the electrolyte, anode, cathode, salt bridge, direction of ion flow and salt bridge and direction of electron flow in the cell. And then right suitable equations for the reactions occurring and classify them as oxidation or reduction. So let's get started with that. So the first thing we're going to do is do our labeling and then we'll do the equation. So we'll start with the electrolyte. The electrolyte is just the solution that's inside. We weren't told in the question what the solutions are but they're solutions of magnesium and nickel solutions. So inside this side we're going to have magnesium 2 plus aqueous and over here we're going to have a nickel 2 plus aqueous. Okay so labeled the electrolyte. Now we need to determine which side is anode and which side is cathode. So if we go back to our activity series that we're told here, we're told magnesium is more active than nickel. So the more active metal is the metal that is oxidized and anode, the anode is the electrode and oxidation occurs. So our magnesium side here so this is going to be our anode. That means the nickel so it's less reactive so it's going to be reduced. So the nickel ions are going to be reduced. So the site of reduction is the cathode. So this is going to be our cathode over here. All right salt bridge. So here's the salt bridge in the middle. Then we need the direction of ion flow in the salt bridge. So there's going to be a positive ion and a negative ion and we need to determine which side they go to. So as the magnesium over here is oxidized you get an increase in concentration of magnesium ions in the solution in the electrolyte. That makes this overall gives it an overall positive charge. So to get rid of that overall positive charge that means the negative ion in the salt bridge has to go in that direction into the magnesium electrolyte. Over here at the other side we're going to get an increase in negative ions as the nickel ions are reduced to solid nickel. So it's going to get an overall build up of negative ions in there. So the positive ion has to go in that direction. We also need to do the direction of electron flow in the external circuit. In our galvanic cell it goes from anode to cathode. So we're getting a whole heap of electrons being generated down here. They don't like each other they repel. So they move away from each other through the external circuit in that direction. So the electron is going this way and then the electron is going that way. The last part of the question says write suitable equations for the reactions that occur in each half cell and classify them as oxidation or reduction. So at our anode we've got our magnesium that's being oxidized. So we're starting with magnesium and oxidation is lost. So the magnesium is losing to electrons. And the magnesium is going into solution as magnesium ions. So it's going in as aqueous. So that means that at our nickel cathode over here the nickel ions are being reduced. So nickel 2 plus aqueous. So the ions are being reduced. They're gaining electrons and you're making a solid nickel. So the nickel ions are coming out of solution. They're being reduced to solid nickel metal. Now we need to identify which one is oxidation. So in this case the magnesium oxidation is lost. So that's oxidation and the nickel ions are being reduced.