Beta Decay - Video Tutorials & Practice Problems

Beta Decay Concept 1

Hey, guys, In this new video, we're gonna take a look at beta decay. Now, we're gonna say that beta decay occurs when an unstable nucleus somehow emits a new electron. Now we're gonna say beta particle can be represented by E for the electron. I like trying here. We're gonna say much smaller than the other two subatomic particles. So the atomic mass can just be understood as zero. And here we're gonna say it. Atomic number is negative one 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 one so an electron is negative one. Now, we're gonna say here beta decay can be represented when we emit a beta particle. So, for example, if we had Mercury and remember the 21 means that's its atomic math. So let's say we had mercury to one. If we look on our periodic table, Mercury has an atomic number off 80. We're gonna emit a beta particle. Now, remember, you're gonna say you're atomic masses have t equal 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 gonna have a mass up to one. And then here we have to be very careful here. This is minus one. So minus one plus what gives me 80. Well, the answer would have to be 81 because 81 minus one gives me the 80 that I had originally. So just remember what? Remember that. So here would be t l. So this would be an example of a beta decay or a beta emission.

Beta Decay Concept 2

Now we're gonna say in terms of size, we know that the Alfa particles are the largest radioactive particle. So we're gonna say beta particles, therefore are smaller than alfa particles now, because they're smaller in size, they're gonna be less damaging if we ingest them. So here they're gonna 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 gonna have mawr penetrating power. And so to stop, you need a sheet of metal or large block of wood toe. Make sure beta particle does not enter inside of our bodies.

Beta Decay Example 1

So here we have to write the balance 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 baited it capture or beta absorption, then it would be a reacted. So here we're starting out with magnesium 25. So that's the atomic mass. On our periodic table. Magnesium has an atomic number off 12. It's gonna emit a beta particle. So our new element that's being created would still have the same atomic mass. And then here, negative one. Plus what number gives me 12. It has to be 13 because 13 minus one gives me the 12 I started out with initially. So this element would be aluminum. Now, Ruffini, Um, are you one? 02 We're gonna see if we look in our periodic table roof in. IAM has an atomic number off 44. Again, we're gonna emit a beta particle, so this number stays 102 And this number here would have to be 45. So it goes upto Rh. Okay, so those were the examples off beta decays or beta emissions

Beta Decay Example 2

now learning from what we covered with Alfa Decane, Beta k thus far, we have to try to answer this question. So here we have led to a weight is formed from thorium 2 32. How Maney, Alfa and Beta decays have occurred. So before even try to answer this question, let's just write down what exactly they're saying They're saying we created led to a weight so led to await It's gonna be a product. And the atomic number of lead, according to our periodic table, is 82 and they're saying it was formed from four E um 2. 32. Thorium has an atomic number off 90. Okay, so what we have to realize next is what exactly does an Alfa decay do? And what exactly does a beta decay do? So remember, in an Alfa decay, we emit Ah, helium particle or an alfa particle. But what does that do exactly to my element? If you go back and look, you should realize that an Alfa decay causes a decrease in your atomic mass, so it decreases atomic mass by four. And what else does it do? It also decreases your atomic number by two So those are the two changes that occur Because again, we're emitting Ah, helium particle or Alfa particle. So if you go from 40 calcium, you admit you admit a healing particle. What do you have now? You're gonna have this is gonna be 18. This is gonna be 36 you have are gone. So what happened? The calcium, its atomic mass, went from 40 to 36. So it lost four its atomic number one from 20 to 18 so it lost to next. Beta decay. What is beta decay due to my element, will you admit a beta particle, which is zero over negative one e So what that does is it increases your atomic number by one. It doesn't touch the atomic mass at all. And that's the key to this question. If we take a look back at our question now, we go from one atomic mass of to 32. One atomic mass of 208 That is a difference of what? 2 30 to minus 20 wait. That's a difference of 24. Beta decay has nothing to do with my atomic mass at all. It only affects my atomic number by increasing it by one. So if I decrease my atomic mass by four. How maney Alfa decays is that so? Remember, every out of the K, we lose four, right? So if we decreased by 24 each off of the case, four lost. So this represents six Alfa decays. Six Alfa decays must have occurred for us to lose an atomic mass of overall. So automatically, the answer is gonna be either a, B or C. Next, what else happens? We're gonna say, OK, if we're losing six off of the case, that means we're losing six. He Liam's right now. What we're gonna say here, we're gonna say six times four gives me 24 and six times to gives me 12. So let's come down here and write down what this is gonna be now. So we're gonna stay here and guys, we're gonna need some room to do this. So let me just take myself out of the image so we have more room to work with. Okay, so we we start out with thorium 2 32/90. We know we're gonna undergo six off of the case, which is a loss of 24 and I'll also 12 from the atomic number. What does this help to create? Well, this helps to create 208 here, and then we're gonna have 78 here. So if you look on your periodic table, look and see what element has 78 we're going to say that that is platinum. Okay, so six off of the case helps us create platinum initially. Now, what's the problem we need now Platinum to go to let remember what happens with beta decay. We're gonna stay with beta decay. Your atomic number changes by one. It increases by one, so you need to go from 78 82. So that's an increase of how much That's an increase of four for your atomic number. So that means you must have had four beta decays occur, So seize our answer. So we're gonna say four beta. The case means what it means that you admitted four of these guys here, which we can just simplify by saying that so you could just say four times zero is 04 times negative. One is negative for here. I'm just combining everything to make it easier for ourselves so you could write it like that. Or you could have just wrote written it. As for over e minus one. E. If you're professor wanted you to write out, the actual reaction would be best to short like this. But since here, I'm just asking you how maney baited a case occurred. You could just simply do it like this to make the math easier and faster to Dio, so see would be the answer. And if we wanted to show this in the best possible way, you come back and rewrite it as 2. 30 to 90 th and you say you have six Alfa decays, plus four baited. The case gives me 20 8/ to let. So if you're professor wants you to show the balanced equation, you have to show it like this. So hopefully you guys were able to realize that fundamentally, what happens with an Alfa decay, your atomic mass decreases by four year atomic number decreases by two. And what happens with the beta decay? Your atomic number increases by one knowing that Alfa decay affect your atomic mass. But beta decay doesn't was the key to answering this question correctly.