 Okay, so let's try one of these radioactive decay problems. So this one, we've got potassium 37 decaying to some particle and some decay particle here. So, does anybody know what this particle is called? You guys remember? So it's an electron that's got a positive charge, so we call it a positive charge. It's like an anti-electron. Okay, so here, right, we've got to add up the masses to 37 and the protons to 19, okay? So here, we've got a plus one charge, right? So this is going to be 18, so that tells us what atom we've got, right? So we look up at the periodic table and we see that it's argon, okay? And what's the mass of argon going to be? Well, over here it's 37, oh, over here it's zero plus something equals 37, so it must be 37. Does anybody know what it is? Or anybody have a problem with that? So we call this a positron decay of potassium 37. Question? So that's not considered fission? No, so this is decay. So fission is when you hit a particle with a smaller particle. So notice we didn't do that here, right? So on the left side of this reaction, it's only this particle here that's decaying, okay?