 Hello, my name is Kevin Conley. I'm an instructor at Foresight Tech, and I'd like to give you another installment of our nuclear chemistry lectures. In this installment, I'd like to tell you about reactions. There are basically two types of reactions that we're going to cover, and they are transmutation reactions and bombardment reactions. I will go over a number of transmutation reactions because they're rather straightforward and common. There are many bombardment reactions, and we will do some examples of those in future lectures. First of all, transmutation reactions always take this form. They have an unstable isotope as a reactant, just like in normal chemistry. And then the unstable isotope will reduce down to a new isotope, or perhaps more than one, and some type of radiation. These then will be the products. And you will spend some of your chemistry time in balancing this. You may be told that you have an unstable isotope and it decays by alpha decay, and you need to find out what the new isotope is by conserving mass and charge. Let's take a look at four common examples. The first example is alpha decay. Here's an example of alpha decay. Alpha decay is, an example of this is you begin with a business nucleus that has 210 as its atomic mass number, and it's going to decay into a helium particle. It's just going to spit right off a helium particle, which is this alpha particle. Alpha is always the 4-2 helium with two protons and two neutrons holding it together. An alpha particle will come out, and then you also get some other new isotope. Well, what new isotope is it going to be? It's rather easy to find out. You take the 83, you subtract 2, you get 81. You look at the periodic table, and you see that that's going to be thallium. The first thing to do is to conserve the atomic number. That way you know the number and the letter, the type of element that you're going to be getting. And this is important because you will recall that the type of element you're dealing with is always determined by the number of protons in the nucleus. So this is the one you should do first. Secondly, we have to find out what the atomic mass number is. Now, the atomic mass number is going to help us find out whether the result itself is going to be stable or unstable in a nuclear sense. Here we have 210. We have to subtract 4. We end up with 206. And then we get this isotope of thallium. The next type of decay we're going to be taking a look at is beta decay. Chronologically speaking, they found beta particles after they found alpha particles. It just so comes out that alpha particles are helium nuclei. And they don't really have a whole lot of energy toward in them compared to beta decay, which beta decay is really electrons coming out of the nucleus. Now, yes, electrons aren't inside the nucleus. But very often, an electron will come out of the nucleus in a way that I mentioned in a previous nuclear chemistry lecture, where a neutron will turn into a proton and an electron. So sometimes, the electrons do fly out of the nucleus. So for example, if you have sodium and it decays through a beta decay, which is well documented, you can look up on a super periodic table and it'll tell you what decay does occur. If it decays, it has 11 plus. And we're going to take away a negative 1, which means we have to add a charge. And recall, if we have a neutron that decays into an electron and a proton, if the electron goes away, the proton stays. Well, the charge of the nucleus has gone up by 1. So we have 11 minus a negative 1 is going to give us 12. So the new nucleus is going to be magnesium. And we know the chemical properties of the product immediately. 25, we're not taking any mass away, because the electron's mass is about 1, 2000 of the neutron or the proton. So 25 minus 0 is going to give us a 25. So we begin with sodium, and we end up with magnesium. And out there someplace goes the electron, or the beta decay. The third type of transmutation reaction we'll take a look at is positron emission. And hopefully, this is familiar to you from the concept of a PET scan, or positron emission tomography. Tomography simply being that they're taking a look at cuts through different parts of the body to make those nice two-dimensional scans. And the way that they do that is they put some type of an element inside, and they take a look at the way the positrons are in fact emitted. In this case, if you have silicon, it will decay by a positron emission. In this case, 14 is the charge. We're going to lose a positron, which is a plus 1. So we have 14 minus a plus 1 is a 13, leaving us aluminum. But the positron is strange. The positron is an electron with a positive charge. It is the antiparticle of an electron. It is very weird, but it's in fact what occurs. So it's a different type of a particle, and it really only occurs during these decays. 14 minus 1 leaves us with 13, 26 minus 0. Because again, if the positron is the antiparticle of the electron, it has no mass in the same way that the beta particle has no mass. 26 minus 0 leaves us with 26. So we go from silicon back to aluminum, and we have these positrons that are zooming out. And very commonly, the positron will meet up with an electron someplace. They'll come together, and you'll end up with just lots of energy, and you'll release gamma radiation, which is just a type of super x-ray that has a lot of energy and can cause a lot of damage. Here we go. Gamma ray emission is the fourth type of transmutation reaction we'll take a look at. Now I want you to, first of all, before we get to the reaction, note that the atomic mass and the atomic mass number of the gamma is a 0. It's not mass. It's not essentially a particle. It's a wave. It's a wave. So if you look at the electromagnetic spectrum, you're going to find television waves, infrared, visible, UVX, and then way over there, you're going to find gamma rays. They're the highest region, the most energetic of all of the waves, and these come from nuclear vibrations. You may be aware that when the electrons go between states 1, 2, and 3 inside the hydrogen atom, they give off photons that have a certain amount of energy, either in the visible or the UV. In this case, we're talking about the things inside of the nucleus vibrating back and forth, and then when they vibrate less, they give off photons. But these photons inside the nucleus are gamma waves, and they have incredible amounts of energy that have so much more energy than the photons that we're used to. Commonly, about 100,000 times more energy. So if you begin with barium, in this case in M, what's called a metastable state, 56 protons barium, we're going to give up a gamma ray which has no charge to it. We're going to end up with barium again. And over here, we go from a 137 metastable, which means that it's excited, and then it's going to lose that vibration energy. And when it does, it gives up the gamma, and it goes back to a stable 137. So essentially, we're not losing any charge or mass. We're just getting rid of that M into a more stable state. It's relaxing the nucleus, and we give off the gamma particles. So it's a little strange, because you're not losing any charge or mass, but you are giving up very important radiation. And as you've seen before on previous lectures, the gammas are the things that cause the most damage, and their reactions do not cause a change in the isotope from which the radiation was emitted. And finally, we have a second type of reaction, not a transportation reaction, but a bombardment reaction. This is what commonly occurs either inside of a particle accelerator, a particle collider, or when light radiation, such as an alpha or a beta particle, is going to interact with other types of material. So for example, if you have two reactants, a beryllium and an alpha particle happens to hit it, we're going to have a 4 plus 2 is going to give us six protons. And those six protons may end up giving us a carbon, for example. And if we have a 9 plus 4, we have a total of 13 nucleons, protons, and electrons. And if we have 13 and the carbon has 12, we've got one left over. And that one left over has to have a charge of 0 to balance our equation. And in that case, this is a neutron. So what happens is if the beryllium is sitting there, it gets hit by the helium. And if the problem tells you there's a carbon remaining, what else is there? That other thing has to be a neutron, because 4 plus 2 is 6, we have a counter for all the protons. 9 plus 4 is 13 minus 12. One's left. That one has to be a neutron with no charge. Thank you for your attention. And we'll get into more detail with these reactions in future lectures.