So this section is where reduction occurs. And that means by definition, it must be our cathode. Now, likewise, when these molecules or ions hit this little electrode, they give off some of these electrons, because electrons want to move from a negative charge to a positive charge. So when this hits it, electrons travel inside this electrode, and they enter our circuit and travel all the way down here. So what happens when electrons leave? Well, this guy is oxidized into diatomic gas, and so it evaporates into our environment.