Intro to Radioactivity - Online Tutor, Practice Problems & Exam Prep

Intro to Radioactivity

Hey everyone. So in our discussion of radioactivity, it's important to remember that radioactivity is just a process of spontaneous decomposition by an unstable nucleus. So remember, decomposition means we're breaking down. We're going to say here that this instability that leads to decomposition is due to excess neutrons or protons in the nucleus, and this in fact creates or produces a new element and in the process we emit some type of radiation.

Now recall that when it comes to an isotope and subatomic particles, there are certain notations you should remember when it comes to R isotope notation, which is this portion here. Remember X represents our element symbol. So for example sodium NA mass number is represented by the variable a atomic number by Z. Now the number of neutrons that you have for your isotope is equal to A minus Z.

Now with this notation, it's also important to remember the notation for the different types of subatomic particles. When it comes to a proton, we could talk about its notation. We'd say for a proton it is 11P. When it comes to a neutron it's going to be 10N. Notice here that our atomic number slot for P is 1 and for the neutron is 0, meaning remember a proton is positive, a neutron is neutral.

When it comes to an electron it's going to be 0-1E. Electrons are incredibly small, so small that their mass really doesn't amount to very much, so their mass number is 0. At the top. Electrons are negatively charged, which is why we have -1 here. And then E for electron. A positron is known as an anti electron or a positively charged electron. So here would still be zero since it's an electron. Doesn't weigh very much, it's an anti electron or positively charged electron, so this will be plus one. Then here we have east.

So this represents what radiation is in terms of radioactivity. We're just breaking down our nucleus because of an excess of neutrons and protons. And here we have our different notations for our subatomic particles.

Nuclear Reactions

Up to this point we've talked about chemical reactions in our earlier chapters. Now we're going to take a look at nuclear reactants. We're going to say the differences between chemical and nuclear reactions are that chemical reactions we have the number and type of elements on reactive and product side being conserved. So basically you start out with five atoms of carbon on the reactant side. You should end with five atoms of carbon on the product side.

This is different from nuclear reactions because with nuclear reactions the identity of elements changes and that's happening because our number of protons are changing. However, with this change, we're going to see that the overall mass number, as well as the overall number of protons is conserved between reactants and products. So let's say you have 5 protons on the reactant side. Your total number of protons on the product side should still stay 5 protons.

In this process though, your beginning element will change identities. So as we delve deeper and deeper into our radioactive decays later on, we'll see how this applies.

Intro to Radioactivity Example

So here in this example question that says label each reaction as chemical or nuclear. Remember in chemical reactions the identity of elements stay the same on both sides, but for a nuclear reaction our elements change identity because we have a changing of the number of protons.

If we take a look at the first one, we're starting out with oxygen 15 and if we look on the other side, oxygen is nowhere to be found. Instead we have fluorine 15 and we actually have a positron. Here the identity of our reactants changed, so this would represent a nuclear reaction.

For our second reaction, we have two magnesium atoms combining with one oxygen molecule to produce two magnesium oxide compound. Here we're going to say we have two magnesiums on both sides and two oxygens on both sides. The identity of our elements have not changed, so this is a chemical reaction or regular reaction.

So this is how we'd identify both of these reactions given to us in this example question.

Understanding Nuclear Reactions

Now, when it comes to a typical nuclear reaction, it consists of apparent nuclei, a donor nuclide and an energetic particle. Here we're going to say that our nuclei is a radioactive isotope that has an unstable nucleus and emits radiation as it decays. Here our parent nuclei is an unstable radioisotope, and this is important. It appears on the reactant side. That's what you start with.

The daughter nuclide is the more stable radio isotope that appears on the product side. So remember apparent births, a child births a daughter nuclide in this case. So we're going to say that we're starting out with the parent. The parent gives off a daughter nuclide, which is more stable. If we take a look here in this example, we have our element X here. It's what we're starting with. This represents our parent. It emits or gives off these two products.

This new isotope Y represents our daughter and here we have. Remember this is an example of a positron, an anti electron. It represents our energetic particle. Now, the energetic partial itself, it can appear as either a reactant or a problem. So that one that really just depends. You have to be on the lookout for the different types of subatomic particles we talked about earlier. They appear on the reactant side of the product side, but when it comes to the parent and the daughter, the parent's going to be the reactant and the daughter's going to be on the product side.

Intro to Radioactivity Example

Here it says to identify the energetic particle in the following nuclear reaction. In this nuclear reaction we have thorium 231. It's going to decompose and it gives us a new isotope. So here this is protactinium 231 and it gives us this element here or this notation.

Here we have an E which stands for electron and -1. So this electron represents our energetic particle. It is on the product side. But remember, when it comes to energetic particles, they can appear in either the reactant side or the product side. You've got to keep an eye out for them, OK?

In this example, this represents our energetic particle.

Types of Radioactivity

Now, there's a lot of types of radioactivity that exists, but when it comes to radioactivity in this course, we're going to say that there are five types of radioactivity. We have alpha decay, we have beta decay, we have gamma emission, and we have positron emission. When we say decay, when we say emission, they're synonymous with each other. OK, they mean the same thing when it comes to decay or omission.

This occurs when your energy particle is emitted from an unstable nucleus and is a product. So each one of these radioactive types have your energy particle as a product. Now with our next one, we call it electron capture, electron capture, so we suction it off from the other four. That's because with electron capture, the energetic particle is absorbed, and because it's absorbed, it's going to be on a reactant side.

So remember, there's five major types of radioactivity you need to remember. Four of them create an energetic particle as a product and the final one, electron capture, has your energetic product at the very very beginning of your nuclear reaction as a reactant.

Intro to Radioactivity Example

So in this example question we have to identify the reactivity as either a decay or a capture. Now for the first one we have carbon 11. It decomposes to give us boron 11 and look our first energetic particle. This is a positron, it's listed as a product. So this would be a decay. Remember, in a decay or mission radioactive process, your energetic particle will be a product.

In the next one what do we have? We have an electron as a problem, so this is also a decay going to two. Here we have our energetic article which is also an electron as a reactant when it comes to a capture type of radioactive process. Capture means that our energetic particle will be a reactant, so this would be a capture.

And the last one, here again is another electron that is also a reactant, so this is also a capture. So remember, with a decay or emission reaction, your energetic particle will be a product. With a capture reaction it has to be a reactant.