Radioactive Decay

Hey guys! In this new video, we’re going to take a look at nuclear reactions. We’re going to say here that nuclear reactions deal with chemical processes that take place in unstable nuclei atoms. Remember your basic picture of the atom. We have spinning around the nucleus are electrons. Within our nucleus, we have our protons and our neutrons. Our protons are positively charged. Our neutrons are neutral.
Nuclear reactions deal with us somehow affecting the number of protons within our given atom. We’re going to say this normally happens with very large bulky radioactive types of elements. We're going to say here unlike normal chemical reactions where the identities of the elements stay the same, we're going to say nuclear reactions often result in elements changing into completely different elements. We're all used to stoichiometry and balanced chemical equations.
For example, we're used to seeing we have H2 gas here plus N2 gas here combine to give us NH3 gas over here. Balancing it here, we’d put a 2 here and a 3 here. But for a nuclear reaction, we’re actually affecting the number of protons within our element. Remember, your protons or your atomic number represents the identity of that element. Every element has its own unique atomic number that no other element has. But in nuclear reactions, we’re actually messing around with the number of protons which results in us creating completely new and different elements. You could start out with calcium 20 and somehow go through some process in which calcium 20, calcium 40 I mean, becomes Argon. That's the whole basis of nuclear reactions. We go from one element to a completely new element by affecting the number of protons. Affecting the number of protons has a direct impact on the identity of the element. 

We’re going to say here when it comes to nuclear reactions, we could think the British physicist Ernest Rutherford who really did a lot of experience with nuclear reactions. His contribution to nuclear chemistry was so great that they actually named element 104 after him. Element 104 is called Rutherfordium. It's kind of umbrage to all the work that he’s done in terms of this field.
Rutherford basically broke down nuclear reactions into three major types of categories. We have our alpha decay, instead of alpha decay you may hear alpha emission. We also have beta decay, which you may also hear as beta emission. Then finally, we have gamma emission. You tend to just hear it as gamma emission. You really don’t hear the term gamma decay.
What does the word decay or emit mean? That means that the radioactive particle will be a product. Remember, if you hear the word decay or emission, that means that the radioactive particle involved in all of these reactions will be a product. The opposite of decay or emitting would be the word capture. Capture would be the complete opposite. Capture would mean that the radioactive particle involved in each of these types of nuclear reactions would be a reactant.
In alpha decay, we emit an alpha particle. In beta decay, we emit a beta particle. In gamma emission, we emit a gamma particle. These particles are what cause our elements to go from one type to another type. What you have to remember is when they say decay or emission, they're saying that this alpha particle, beta particle, or gamma particle will be a product. But if you hear the term capture or even absorption, then that means that the alpha particle, the beta particle, and the gamma particle will be reactants. This has a profound difference on what exactly your products will be because you'll be emitting or decaying these particles along with a whole new element with it.
The farther into this chapter we go, we’ll learn that beyond these three, we also have positron emissions as well as electron capture. Those will come after we learned these first three major types. Just remember, in a regular chemical reaction, we start out with let’s say carbon, we end with carbon. But in the nuclear reaction, we’re emitting or capturing radioactive particles. As a result, that's going to change the identity of my element. You can start out with calcium and end up with something completely different like Argon. 

Hey guys in this new video, we’re going to take look at Alpha Decay.
So, remember Rutherford talked about the 3 major types of decays. There’s alpha decay, beta decay and gamma emission.
Here, we have alpha decay. We’re going to say alpha decay occurs when unstable nucleus emits a particle composed of 2 protons and 2 neutrons. Now, just think about it, we say that our atomic mass equals the number of protons plus the number of neutrons. So here our atomic mass is, we lose 2 protons and 2 neutrons. So, 2 plus 2 gives me 4. Atomic Mass = number of protons + number of neutrons = 2 + 2 = 4
Your atomic mass is protons and neutrons added and your atomic number is just the number of protons. So, the number of protons loss is 2.
Atomic number = number of protons = 2
So, we’re going to say the alpha particle is represented by 4 for your atomic mass over 2 your atomic number and here we have our alpha symbol α.
24 α
Now we can also say that on our periodic table, we have an element that also has as atomic mass of 4 and an atomic number of 2. That element is Helium, 24He. So, we can say that the alpha particle can also be represented by the element Helium because Helium has the same atomic mass as an alpha particle and has the same atomic number as an alpha particle.
And remember, we’re using the term decay. So, decay means that this alpha particle will be our product.
So if you want to take a look at an example of this, we can think of for examples on your periodic table. You could have Polonium which in your periodic table is Po. Polonium, we’re going to say let’s talk about isotope 210.
Polonium (Po) – 210
Now, remember what these nuclear reactions. They can happen with different isotopes of an element. So, on your periodic table we’ll be doing different types of decays with different types of isotopes. So, don’t worry if your atomic mass on your periodic table doesn’t match my atomic mass. That’s because I am dealing with a certain isotope of that element. Remember, isotopes have the same atomic number, so they’re the same element, but they have different number of neutrons, so we have different atomic masses.
So, here Polonium 210 means the atomic mass is 210Po. If you look on your periodic table, Polonium has an atomic number, number of protons, of 84.
84210Po
Now, we’re going to undergo alpha decay. Alpha decay means we’re going to spit out or emit an alpha particle. You can represent it like this 24 α or like this 24He.
Here I’ll just choose to show it as Helium. So, we’re going to emit 4 over 2 Helium.
84210Po  24He
Now, nuclear reactions are different from regular reactions, but there are some similarities. Just like you have to have a regular chemical reaction balanced, you have to have a nuclear reaction also balanced.
So, here our total atomic mass is 210. Here we have already an atomic mass of 4. So, we need to create an element that when I added to the 4 gives me back this mass of 210. So, the new element has to be 206 because 206 + 4 gives me 210. Also, your atomic numbers need to match on both sides. This atomic numbers 2, we need it to add up to 84. So, it say that the new element would have to have 82 because 82 + 2 gives me 84. And what element would that be? Well that would be lead.
So, what we’d say here is that we’d say the alpha decay of 210Polonium creates a brand new element 206Lead.
84210Po  24He + 82206Pb
The Helium were the alpha particles that just something that we emit, that’s just waste. The new element that we’re concerned with is the Lead 206. So, this represents an alpha decay, and it’s as simple as that. Make sure that your atomic masses add up on both sides. Make sure your atomic numbers add up on your both sides.

Now, if you want to talk a little bit more about this alpha particle. We’re going to say: In terms of the size of radioactive particles, alpha particle is the largest.
So, it’s bigger than your beta particle, it’s bigger than your gamma particle. So, your alpha particle is the largest of them. It is the most damaging on biological cells because it has the highest ionizing power.
Which means that somehow, if you got it into your body, that it will just shred your insides. It will irradiate all of your biological cells in your body. A person who is exposed to an alpha particle internally has very low chance of survival. The good thing is, because it has the highest ionizing power, and because it’s so large, it’s extremely difficult for it to penetrate us. Penetrate our skins and get into ourselves.
So we’re going to say: They have the lowest penetrating power and can be stopped by clothing and by the air of our environment.
We’re going to say that our clothes, even the air around us provides protection against alpha particles getting into our bodies.
Now, how could you get an alpha particle inside of you? Maybe you work in a nuclear facility, where you have contaminated water or contaminated food or there was some chemical leak and it got exposed in our environment in some way and then you ingested it. But, it is extremely hard for things like this to occur. So, alpha particles are extremely damaging to our insides, but the good thing is they’re extremely hard to get into our bodies.

Hey guys in this new video, we’re going to take a look at Beta Decay, now we’re going to say that Beta decay occurs when an unstable nucleus somehow emits a(n) electron. Now we’re going to say beta particle can be represented by e for the electron. Electron here we going to say is much smaller than the other 2 sub atomic particles, so the atomic mass can just be understood as 0e and here we going to say atomic number is -1 0e because the atomic number is basically the number of protons since this is an electron, we’re going to say that it’s the opposite of a proton which is 1 so an electron is -1.
Now we’re going to say here Beta decay can be represented when we emit a beta particle so for example if we had Mercury 201 and remember that 201 means its atomic mass, so let’s say we had Mercury 201 if we look on our periodic table, Mercury has an atomic number of 80. We’re going to emit a beta particle 1 0e, now remember you’re going to say your atomic masses have to be equal to each other on both sides of the arrow and your atomic numbers as well. Here the electron has no mass so the new element is going to have a mass of 201 and then here we have to be very careful here this is -1 so - 1 + what gives me 80? Well the answer would have to be 81 because 81 - 1 gives me the 80 that I had originally. So just remember that. So here would be Tl so this would be example of beta decay or a beta emission.

Now we’re going to say in terms of size, we know that the alpha particles are the largest radioactive particle, so we’re going to say beta particles therefore are smaller than alpha particles. Now because they’re smaller in size they’re going to be less damaging if we ingest them. So here, they’re going to have a lower ionizing power but the problem here is because they’re smaller they’re able to better penetrate into our skin. So here they’re going to have more penetrating power and so the stopping sheet of metal or large block of wood to make sure beta particle does not enter inside our bodies. 

So, here we have to write the balanced nuclear equations for each of the following beta emissions, again, beta decay, beta emissions means that the beta particle will be a product, if they had said beta capture or beta absorption then it would be a reacted.
Example 1: So here were starting out with Magnesium 25, 25Mg so that’s the atomic mass.
On our periodic table Magnesium has an atomic number of 12.
1225Mg  -1 0e +1325Al
It’s going to emit a beta particle, -1 0e , so our new element that’s being created would still have the same atomic mass, and then here -1 + what number gives me 12? It’d have to be 13, because 13 - 1 gives me the 12 I started out with initially. So this element would be Aluminum (Al).
Now Ruthenium (Ru) 102, were going to say if we look on our periodic table Ruthenium has an atomic number of 44.
44102Ru  -1 0e +45105Rh
Again were going to emit a beta particle so this number stays 102 and this number it would have to be 45. So goes up to Rh.
Ok, so those are the examples of beta decays or beta emissions. 

Hey guys, in this new video, we’re going to take a look at electron capture. The word capture, we've been talking about this. There's decay and emission versus capture. Decay and emission means that your particle will be our product. But capture means it will be a reactant. Here we're talking about an electron. Remember, an electron is really just a beta particle. When we say electron capture, we’re really saying beta capture. They're both dealing with an electron. Beta decay, the electron will be a product. But in beta capture or electron capture, it'll be a reactant.
Here we’re going to say electron capture involves the absorption of an electron which remember, we saw as this symbol, by an unstable nucleus and is represented by the following reaction. Let's think of an example. We could deal with it francium, which is the metal most to the left and the lowest down group 1A. That’s Fr. Here we’ll say we’re dealing with isotope 223. Here capturing at this electron is not going to be a product, but it's going to be a reactant. We're going to have francium-223 and francium has an atomic number of 87. We're going to absorb an electron. What effect does that going to do? That's going to be 223 plus 0 gives me 223. Then 87 minus 1 is going to give me 86. It’ would become radon, Rn. That represents the opposite of beta decay. Instead of doing beta decay or emission, we're doing beta capture AKA electron capture.

Hey guys! In this new video, we’re going to take a look at positron emission. Here, we're going to say positron emission occurs when an unstable nucleus emits a positron.
What's a positron? A positron is an antiparticle of the electron. Remember, the electron is represented by this. A positron is the opposite of that. It looks like an electron but instead of it having a negative sign, it'll have the opposite sign. It will be a positive electron. A positron is considered just a positive electron. I know this is weird but again, remember we're dealing with nuclear reactions. A lot of unaccustomed things that we are not used to seeing do occur. One of them is this positron. We’re going to say here, here’s our positron. Because we're talking about the word emission again, emission would mean decay which means that this positron would be a product.
Let’s think of an example. Here, Einstein has his own element named after him, Einsteinium. We’ll deal with isotope 253 of Einsteinium. Einsteinium is Es on our periodic table. It has an atomic number of 99. We're going to emit a positron and because we're emitting a positron, let’s see. Because the atomic mass is 0, the new element is still going to be 253. But because the bottom is one, what number plus 1 gives me 99? It’d have to be a 98. Here, that would just be Cf. This would be an example of a positron decay or positron emission.

Based on that, let's answer these two questions. It says: Write balanced nuclear equations for each of the following positron emissions. Again, your positron will be a product. Here we're dealing with uranium 235. Uranium is U. On your periodic table, it's going to have an atomic number of 92. We emit a positron so this is going to be 235 and 91 plus 1, it gives me 92. 91 would be in Pa.
Next one is radon which is Rn. Radon has an atomic number of 86. We emit a positron so now the element is still going to be 222 and 85 plus 1 gives me 86. That's actinium. These would be two examples of our positron emission.