Alpha Decay - Online Tutor, Practice Problems & Exam Prep

Alpha decay is a type of radioactivity where an unstable nucleus emits an alpha particle, consisting of two protons and two neutrons, equivalent to a helium-4 nucleus. This process often occurs in heavy nuclei to produce a more stable atom. In balancing nuclear reactions, it's crucial to maintain equal mass numbers and atomic numbers on both sides of the equation. For instance, platinum-171 decays to form osmium-167 and an alpha particle:

${\mathrm{Pt}}^{171}\to {\mathrm{Os}}^{167}+{\alpha }^4$

Alpha particles, being large, have high ionizing power but low penetrating power, meaning they can cause significant damage to biological tissues if ingested or inhaled, despite being unable to penetrate the skin. Protective measures include clothing, paper, and even air, which can shield against these particles. Understanding the balance of nuclear reactions and the implications of alpha particle emissions is essential for safety in environments with radioactive materials.

Alpha Decay

Now here we're going to say that alpha decay occurs when an unstable nucleus emits an alpha particle. Now what exactly is an alpha particle? Well, an alpha particle consists of two protons and two neutrons. So let's think about this. If it's two protons, that means that its atomic number would be two. And remember for your mass number that comes from adding together your number of protons and neutrons together. That's why we have 4 here and four here.

If you look on the periodic table, you'd see that the element that has an atomic number of two is helium. So here we're dealing with helium, but we just did that. It's an alpha particle, so you can also represent it with the alpha symbol. So an alpha particle can be represented by Helium 4 or by the alpha symbol. Here we're going to say this typically occurs in heavy nuclei with excess protons and neutrons. Later on, we'll classify what exactly constitutes a heavy nucleus. Now here it produces a stable helium atom, which is in this case helium 4 isotope.

Now when balancing nuclear reactions of any type of radioactivity, we must always balance the atomic number which is the number of protons, as well as the mass number which remembers the number of protons and neutrons together and you have to be balanced on both sides. If we take a look here, we have our basically our parent nuke line which is platinum, platinum 171. It's going to decay or breakdown and produce an alpha particle. Remember we need to make sure that the overall mass number on both sides are equal and the overall number of protons on both sides are equal.

Here on the reactant side we have 171. Our alpha particle gives us 4. The product site still needs to add up to 171 though. So we think about it, what number would I place here that would add word for and give me 171? Well, 167. So our new winesettu that we're making has a mass number of 167. Let's look at the reactant side. Our parent is 78. Our alpha particle is already giving us 2. But remember the total number of protons have to be the same on both sides. If your alpha particle is giving us 2 already, what number do I have to place here in order to get 78 at the end? 76.

Remember your atomic number. The number of protons is unique to the element. So look on the periodic table. What's the only element on the periodic table that has an atomic number of 76? So here that would be Osmium O. Here we say that our latinum 171 isotope undergoes alpha decay to produce osmium 167 plus an alpha particle. Osmium is a pretty interesting metal when it comes to periodic tables, one of the most dense elements on the periodic table. So that's just some extra information. It's not really important to this question to get the answer, just want to give you guys that piece of trivia.

All right, so here we've just shown an alpha decay for our first isotope, and this is the way you have to do it. You have to make sure that your mass number has to be the same on both sides. On the reactant side, it's 171, so it needs to add up to 171 on the product side, the total number of protons is 78 on the reactant side, so you have to add these together to get 78 again. OK, so make sure the number of protons and mass numbers are the same on both sides of your nuclear reaction. That's how we balance them.

Alpha Decay Example

Here it says to write a balanced nuclear reaction for the alpha decay of radium 204. Alright, so here we're undergoing alpha decay, so we have radium 204. Alpha decay means that we're going to produce an alpha particle which is He42 or helium.

Now remember the mass numbers on both sides have to equal. The number of protons on both sides have to equal. We have 204 on the reactant side, so on your product side it needs to also add up to 204. We already have 4 coming from the alpha particle, so we need an additional 200. So 200 + 4 gives me 204 on the product side.

On the reactant side we have 88 protons with radium. We need 88 protons on the product side, two of them already coming from the alpha particle. So to get to 88 our new lines in total has to have 86. 86 + 2 gives me 88. Look on the periodic table and that would be Radon RN.

So this would represent the alpha decay of radium 204. It produces an alpha particle and our new isotope of radon 200. OK, so this would be our final answer.

Characteristics of Alpha Particles

Now when it comes to our energetic particles, we have to talk about their ionizing power and their penetrating power. Now ionizing power is the ability of an energetic particle to it's in a name ionize atoms and molecules. Penetrating power is the ability of an energetic particle to pass through matter. Now with these energetic particles, it's important that we shield ourselves from their effects because if they can get into our bodies, they start ionizing molecules and atoms inside of us. It can lead to some very dangerous and disastrous results.

So here we're talking about the alpha particle, let's talk about its particle symbol, and we know that it is 42 and then the alpha symbol or the helium symbol. Here we have basically our alpha decay reaction, which is the platinum 171 isotope decomposing to give us osmium 167. In terms of size, we say that the alpha particle is the largest of our energetic particles. Because it is the largest, its ionizing power is the highest. Now, luckily, because it's so large, it's hard for it to penetrate our skin. So we're going to say that it has the lowest penetrating power.

Now, what can shield us from the effects of an alpha particle? Well, because they're so large, it's easy to stop them in their plates. They can't get through nooks and crannies and crevices because they're so large. So things such as clothing can protect us from an alpha particle. Our skin, our skin is strong enough and and thick enough, and the alpha particle being so large it can't penetrate our skin. We can also say paper, even the air around us can act as a shield against alpha particles.

Now here we're going to say because of high ionizing power, alpha particles are considered the most damaging to biological tissues. Remember, they're very large. So because they're large, they're going to move very slowly if they get into our system, giving them ample time to ionize everything around them in terms of our biological tissue. So it's always imperative to make sure that something like this does not enter our bodies.

How could it enter us? Well, maybe alpha particles. You're in a nuclear facility or something and alpha particles contaminate your food and you ingest it. Can't protect yourself from that. Once you consume the food and it's inside of you, then again it can lead to very dasp like dangerous and disastrous results. Alright, so just keep in mind these fundamental ideas when it comes to the alpha particle in terms of its ionizing power and penetrating power.

Alpha Decay Example

Here it says select the correct statement by alpha decay. Here the parent nuclide gains 2 protons and two neutrons. No, one doesn't gain them and loses them. To create the alpha particle produces radiation by absorbing A helium nucleus. No, it doesn't absorb the helium nucleus. It emits or gives off or loses the helium nucleus. That's what the alpha particle is.

Alpha particles can easily penetrate cells well. In terms of size, the alpha particles are the largest, so it's hard for them to penetrate our skin and therefore penetrate ourselves as easily when alpha part. When alpha decay occurs in an unstable atom, the mass number decreases by 4 and the atomic number decreases by two. This is true because what are we losing? We're losing 2 protons and two neutrons.

2 protons being lost would lead to a decrease of our atomic number by two, and losing 2 protons and two neutrons would give us a mass number of four. So your mass number would decrease by 4. So here option D is a true statement.

Here’s what students ask on this topic:

What is alpha decay?

Alpha decay is a type of radioactive decay in which an unstable atomic nucleus emits an alpha particle and transforms into a lighter nucleus. An alpha particle is composed of two protons and two neutrons, which is the same as a helium-4 nucleus. When an alpha particle is emitted, the original atom loses four units of mass (since the alpha particle has a mass number of 4) and two units of positive charge (since it has two protons).

This process decreases the atomic number of the original element by two, leading to the formation of a different element that is two places to the left on the periodic table. For example, if uranium-238 undergoes alpha decay, it will emit an alpha particle and become thorium-234.

Alpha decay typically occurs in the heaviest elements where the strong nuclear force is not sufficient to hold the nucleus together against the repulsive forces between protons. The emitted alpha particles have relatively low penetration power and can be stopped by a sheet of paper or even the outer layer of human skin.

Which missing item would complete this alpha decay reaction?

To complete an alpha decay reaction, you need to know that an alpha particle consists of 2 protons and 2 neutrons, which is equivalent to a helium-4 nucleus (⁴He). During alpha decay, an atomic nucleus emits an alpha particle and transforms into a new nucleus whose atomic number is reduced by 2 and mass number by 4.

The general equation for alpha decay is:

X Z A → Y Z-2 A-4 + He 2 4 Here, XZA is the parent nucleus (the original unstable nucleus), YZ-2A-4 is the daughter nucleus (the new, more stable nucleus), and He24 is the emitted alpha particle.

So, if you have an alpha decay equation with a missing item, you would identify the parent nucleus and subtract 2 from its atomic number and 4 from its mass number to find the daughter nucleus that completes the reaction.

What happens during alpha decay?

Alpha decay is a type of radioactive decay where an unstable atomic nucleus emits an alpha particle and transforms into a lighter nucleus. An alpha particle consists of two protons and two neutrons, which is essentially a helium-4 nucleus. When an atom undergoes alpha decay, its atomic number decreases by two, and its mass number decreases by four, reflecting the loss of the two protons and two neutrons.

For example, if you start with an atom of uranium-238 (which has 92 protons), after alpha decay, it will transform into an atom of thorium-234, which has 90 protons and a mass number reduced by four. This process releases energy, which is carried away by the alpha particle. Because alpha particles are relatively large and carry a double positive charge, they interact strongly with matter and have a short range. This means they can be stopped by a sheet of paper or even the outer layers of human skin and pose little hazard unless ingested or inhaled.