 Our video lesson now is nuclear chemistry. In particular, we will deal with nuclear reactions. We have essentially gotten to the real chemical aspect of nuclear chemistry because we will be dealing with reactions. We will have reactants and we will have products. In virtually all cases, we will have only one reactant because it will decay into multiple products. We will characterize these reactions according to what type of radiation will occur or be emitted into the reactants. First of all, all of these reactions will begin with an unstable isotope. The unstable isotope will then be reduced to a new isotope which may or may not be stable itself plus some type of a radiation. This process is called either transmutation or radioactive transmutation for long form or a decay or a nuclear decay for long form. There are a number of examples. First of all, the most common is the alpha decay. An alpha decay is a case when an alpha particle is emitted. An alpha particle is simply a helium nucleus. If you take a look at the numbers, written up high, we have the atomic mass number which is the combination of protons plus neutrons. Here you can see that the numbers always add up like in a chemical reaction. 210 equals 4 plus 206. Bismuth has a total number of protons and neutrons equal to 210. Helium has 4 protons plus neutrons. And thallium has 206 protons plus neutrons. At the same time, underneath we have the atomic number, the number of protons in the nucleus. The number of protons in the nucleus tells us which element we're dealing with. If you have 83 protons, this is bismuth and it's always bismuth. If you have two protons, this is helium and it is always helium. If you have 81, it is always thallium. And you can see 83 equals 2 plus 81. So if you begin with bismuth, it will naturally decay to an alpha particle, a helium nucleus, plus thallium. That is alpha decay. Another type of decay, which is quite common, is beta decay. An example of beta decay is sodium decaying into a beta particle plus magnesium. A beta particle actually is just what we call an electron. But it's historically called beta decay because it was the second decay that was put on record and identified back between about 1898 and 1910. So if you take sodium and you begin with 25 protons plus neutrons, we will go to, well, zero. The electron doesn't have a proton and the electron does not have a neutron. So we'll move all those protons and neutrons over the magnesium, just like this. We have 11 protons here and then negative 1. What does that mean? Well, actually it doesn't mean we have negative 1 protons. It means we have a charge of negative 1 because this is an electron, as mentioned before. So somehow, how did we have 11 protons and we end up with, this is strange. Well, as I've mentioned in a previous video, the neutron is not a stable particle. The neutron will naturally decay when isolated during a path of about 12 minutes when it's alone because it gets pretty lonely into a proton plus an electron plus energy. But inside of a nucleus, this process occurs much more slowly so you can see that the neutron will decay into a proton plus an electron. So reactions like this will cause electrons to be ejected from the sodium and as a result a proton will be created. This is then beta decay when an electron is emitted. Related to beta decay when an electron comes out, we have something called positron emission. Positron emission was quite a mystery when it first did occur because nobody really understood what a positron was. Positrons were really understood a bit later during the 60s during the period of particle research that was introduced to in a previous video. And positron emission tomography or PET PET scans began to be used in the 90s for medical applications. There for example, silicon will decay into a positron as its radiation plus magnesium. We have 26 protons and neutrons in silicon. We don't have any protons or neutrons in the positron and we will get a magnesium with 26 protons and neutrons. We begin with 14 charge, the positron takes away a positive charge and then we get a magnesium with 13 protons left. This then is positron emission which is weird much like beta emission is weird. But hey, we didn't make the universe, we just live here. Gamma radiation is what comes next and you have to be careful with gamma radiation because although there is a radiative decay, it doesn't have any mass. So it's not like an alpha particle or a neutron or an electron, it's just like a flash of lightning. It's a bolt of energy. And the problem with this bolt is that bolt of energy left my hand like the marker. The energy has a location, that's pretty weird. But in any event, the gamma decay is going to be like taking a barium, releasing this big chunk of energy and it's a big chunk of energy and you get another barium back out. We're not changing the mass, 137 is 137, 56 is 56. The mass doesn't change, the number of particles doesn't change but a lot of energy is released. So what does that mean? Well, it's like being in a very high excited state and then you chill out. Where does the energy go? It leaves. Which is why often a product that is in what's called a metastable state or a very excited state will decay to another state, may or may not be stable itself but essentially this one just has a lot of energy in the nucleus and it will give up that lot of energy in the nucleus in the form of gamma radiation. And as explained in previous videos, these gammas have a lot of energy, they have a lot of power and they're very good for creating semiconductors and different types of material but they also have a very significant impact on the human body. There's a lot of energy that is given off, as I've mentioned, in the marker and it also has a specific position so it's strange. It's often called a gamma particle because it has energy, particle that is just energy and no mass, sorry, particle that is energy with no mass but it's mostly called a particle because it has a simple location. Finally we come to bombardment which is a reaction. It's not really a transmutation because no new type of particle radiation is essentially given off. What you do is, it's not a decay I guess is what I'm trying to say. The bombardment reaction for example is if you take beryllium and you hit it so we have two reactants in this case. If you take beryllium and you hit it with an alpha particle, one of these, what you're going to get is you're going to get very stable carbon and you're going to get a neutron. The point with the neutron is once you create a neutron you can use it to probe lots of different things. These are very good for use in creating semiconductors, they're very good for use in nuclear reactions and they also can be very good for doing different medical probes. In this case these reactions were understood by the experiments done in the 60s during colliders. They continue to be done for different types of research and they have many different types of medical applications. Thank you for your attention.