Band of Stability: Alpha Decay & Nuclear Fission - Online Tutor, Practice Problems & Exam Prep

Radioactive isotopes, which are unstable due to an imbalance in neutron and proton numbers, undergo processes like alpha decay and nuclear fission to achieve stability. Alpha decay occurs in isotopes with atomic masses ≥ 210 amu, emitting an alpha particle to reduce nucleons and move towards stability. Nuclear fission involves bombarding an isotope with a neutron, releasing vast energy and splitting the atom into lighter, stable nuclides. This process can trigger a chain reaction, producing more neutrons that perpetuate the reaction. Both mechanisms help isotopes reach a more stable state within the band of stability, with fission also harnessing significant energy release.

Intro to Band of Stability

Now before we talk about alpha decay and nuclear fission, it's important to understand that isotopes that lie outside the band or valley of stability are considered unstable radioactive isotope. And we're going to say these isotopes will alter their number of neutrons and or protons to move closer to the band or valley of stability.

Now we know they do this predominantly based on our header that they do it through alpha decay and nuclear fission, but they can also do it through beta decay. They can do it through electron capture or even positron emission. So these are just the different avenues that our particular isotope can take in order to get closer and fall within the band of stability and reach a greater level of nuclear stability.

So keep this in mind when looking at any isotope and comparing it onto the neutron to proton plot.

Band of Stability: Alpha Decay

Here we're going to say that alpha decay happens for isotopes. In the top right corner of the neutron deproton plot, we are going to say these isotopes have an excess of neutrons and protons. If we take a look here, we have platinum 213. Here it lives within our red region, which means it wants to do alpha decay in this case.

Here we have alpha decay of platinum 213. It would emit an alpha particle as a product and as a result it will create Bidsmith 209. By doing this, we're going to say, what does it do? Well, if we look at our plot, we know that on our Y axis we have our number of neutrons. On our X axis we have our number of protons. Here it's decreasing its number of neutrons, decreasing its number of protons so that we can fall within the band or valley of stability and create a more stable isotope.

This in this case would be bismuth 209. It's giving us this green dot right here. Now this happens with isotopes with atomic masses of that are equal to or greater than 210 AMU. We're going to say this whole process is just helping to decrease the total number of nucleons, your total number of protons and neutrons, because there's an excess of both of them. OK, so in this case again removing from the top right section this red area into the more stable green area which represents our band or valley of stability.

Band of Stability: Alpha Decay & Nuclear Fission Example

Here it says which daughter nuclide would resign in the band of stability created from the alpha decay of lead 212. All right, so lead 212 lead is PB and 2:12 is its mass number. If we look on the periodic table, we'll see that the atomic number of lead is 82. We're told that it's undergoing alpha decay, so we're gonna produce an alpha particle as a product.

We are mass numbers to be the same on both sides, and our total number of protons will be the same on both sides. We have 212 on the reactant side, so we need 212. On the product side, we already have 4, which means we need another 208. Here we have 82 protons. On the reactant side we need 82 protons. On the product side we already have two from the alpha particle, which means we need another 80 from our new isotope.

If we look on the periodic table, the element that has an atomic number of 80 would be Mercury HG. So we've just created Mercury 208. So option B would be our final answer.

Pb 212 → Hg 208 + α 4

Band of Stability: Nuclear Fission

Under nuclear fission we're going to shoot a neutron at the nucleus of an isotope and from this we're going to release an extremely large amount of energy. So this is a man made process with the main objective is extracting as much energy in this process. Now an additional benefit to this is that large heavy elements, those that are greater than 209 AMU, so the radioactive ones can be split into two lighter daughter nucleides. Here this will help to drastically lower the total number of nucleons, so protons and neutrons for an isotope.

So herefore we take a look at this image. We're going to say that under nuclear efficient again, we inject a neutron into the nucleus of an isotope. The isotope in question is plutonium 239. Remember, neutron has the mass number one, and since it's neutral, its atomic number is 0. When we inject this neutron into plutonium 239, we create a very unstable plutonium 240. This becomes our parent nuclei here. It's this that undergoes nuclear fission.

If we're to take a look at the neutron of proton plot, we see that the plutonium 240 is deeply in the red section of the plot and we're going to say it undergoes nuclear fission. It's going to break apart. It breaks apart to give us zirconium Zr103 and barium Ba134. In addition to this it's going to give us 3 neutrons and our main objective, all of this energy, so 207.1 mega electron volts, which is an incredible amount of energy.

Now, another thing that happens because of nuclear fishing is that we create these three neutrons. What started this whole process? A neutron. A neutron was injected into the nucleus of a plutonium 239 acetone. We just created three additional neutrons, each of those neutrons that seek out another plutonium, 230, not 239, and start this process all over again, creating more daughter isotopes, products and even more energy. And this could keep going on and on and on, which is why we say that this can do a chain reaction.

OK. So the newly created neutrons further react, they can further react with additional plutonium 239. Alright. So what effect does this have in terms of our plot? Well, we see that we had our plutonium 240 over here and it created two daughter isotopes as products which fall within the band of stability. So we help to create two more stable isotopes as a result, right. So again, our primary objective is to create energy and create a ton of energy through chain reaction. But an added benefit to this is that we create daughter product nuclei, nucleines that are within the band of stability, something that's even more stable, right. So keep this in mind when we're looking at a nuclear fission reaction.

Band of Stability: Alpha Decay & Nuclear Fission Example

Now, nuclear fission is a commonly occurring process for uranium 235, providing the identity of the missing daughter nuclide produced at the end of the reaction. All right, so we injected a neutron to uranium 235, which created uranium 236, which is unstable and it undergoes nuclear fission. We see the energy that's produced. We see one of the daughter products and we see our three neutrons being created.

Remember that your mass number, total mass number on both sides have to be the same and your total number of protons on both sides have to be the same. Here we have 236 on this reactant side here and we need 236 on the product side. Well, we have 141 here and then 3 * 1 is 3 so so far we have 144. What number do we need to have for A to also have a total mass number of 236? So 236 - 144 will give me 92, so here it would be 92.

And then if we look at the number of protons we have 92 on the reactant side here this is 0, so it doesn't contribute. Here we have 56. So if we do 92 - 56 here, that'll give me my number of protons as being equal to 36. If we look on the periodic table, what element has an atomic number 36 and be Krypton. So here this would be Krypton 92 which gives me option B as my correct answer.

Which of the following is a potential daughter nuclide created from the nuclear fission of uranium-233 that resides near the band of stability? 

a) Strontium-94     

b) Radon-222

c) Curium-247

d) Thorium-232

• A. Strontium-94
• B. Radon-222
• C. Curium-247
• D. Thorium-232