Unit 5 lab practical – Radioactive decay

Part 1 - Vocabulary: Define the following terms in your own words.

1. Decay:

2. Nuclear:

3. Isotope:

4. Particle:

5. Proton:

6. Neutron:

7. Electron:

Part 2 - Prior Knowledge Question: (Do this BEFORE starting the practical.)

The chart below gives the locations, charges, and approximate masses of three subatomic particles. The approximate mass of each particle is given in universal mass units (u).

1.   The massnumber of an atom is equal to the sum of protons and neutrons in the nucleus.    A helium atom has 2 protons and 2 neutrons. What is the mass number of this atom? _____

2.   The atomicnumber of an element is equal to the number of protons in each atom of the element. All helium atoms have 2 protons. What is the atomic number of helium? _____

Part 3 – Alpha decay:

Whilst most atoms are stable, some are radioactive – this means they have a tendency to undergo spontaneous nuclear decay. The decay of radioactive atoms will often result in the emission of particles and/or energy. There are 3 main categories of radioactive decay: alpha (α), beta (β), and gamma (γ).

You can explore the first of the radioactive decays here:

https://phet.colorado.edu/sims/cheerpj/nuclear-physics/latest/nuclear-physics.html?simulation=alpha-decay

0.   To begin:

A.  Load up the simulator – note that the first time you open it, it may take a few minutes to get started. Open this sim on your web browser – this may not be iPad compatible so you will need access to a computer/laptop in order for this to work.

B.  Select “single atom” view and make sure that polonium-211 is selected as the atom of choice.

C.  When you are ready, click “reset all” in the bottom right corner to get a fresh start.

1. Describe: Using your foundational knowledge, describe the following characteristics:

What is the atomic mass of Polonium-211 have?

Using a periodic table, calculate the following:

How many protons does Polonium-211 have?

How many neutrons does Polonium-211 have?

2. After polonium-211 decays, what stable nucleus is formed?

Has the atomic number changed? What about the atomic mass?

3. Pause the simulation immediately after the decay occurs. What is being emitted by the polonium-211 nucleus? (There are 2 emissions).

What is the particle emission made of?

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4.   Click ‘ reset all’ and run the simulation again – what is the half life of a polonium-211 atom?

5. Calculate: Look at the following equation below. What you see is the original polonium atom on the left. The boxes on the right represent the daughter product—the atom produced by radioactive decay—and the emitted particle.

Using your understanding from the questions above, fill in the blanks with the daughter product and the emitted particle.

Next, click on Multiple Atoms in the simulation. Add all 100 polonium-211 nuclei to the simulation by adding 10 nuclei to the simulation at a time under the Bucket o’ Polonium. Once you have all 100 added, click on Reset All Nuclei.

6. After you click on Reset All Nuclei, the simulation starts over again. By when do you expect most of the polonium-211 nuclei to decay?

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7. Pause the simulation at the half-life marker. In the upper left-hand corner, there is a pie chart and a data table. How many polonium-211 nuclei remain after one half-life? How many lead-207 have been created?

8. Click ‘reset all nuclei’ , and pause the simulator after every 0.5 seconds. Note the number of polonium-211 nuclei present. Fill in the data chart below, and create a graph of polonium-211 nuclei versus time.

What shape does this graph have? Does the polonium-211 decay at a constant rate or does the rate decrease over time?

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Part 4 – Beta decay:

Next, we will be looking at a secondary type of decay known as beta decay. You can explore beta decays here:

https://phet.colorado.edu/sims/cheerpj/nuclear-physics/latest/nuclear- physics.html?simulation=beta-decay

0.   To begin:

A.  Load up the simulator – note that the first time you open it, it may take a few minutes to get started. Open this sim on your web browser – this may not be iPad compatible so you will need access to a computer/laptop in order for this to work.

B.  Select “single atom” view and make sure that carbon-14 is selected as the atom of choice.

C.  When you are ready, click “reset all” in the bottom right corner to get a fresh start.

1. Describe: Using your foundational knowledge, describe the following characteristics:

What is the atomic mass of carbon-14 have?

Using a periodic table, calculate the following:

How many protons does carbon-14 have?

How many neutrons does carbon-14 have?

2. After carbon-14 decays, what stable nucleus is formed?

Has the atomic number changed? What about the atomic mass?

3. Pause the simulation immediately after the decay occurs. What is being emitted by the carbon-14 nucleus? (There are 3 emissions).

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The particle emission comes from the breakdown of a neutron into a proton – explain this process:

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4. Calculate: Look at the following equation below. What you see is the original polonium atom on the left. The boxes on the right represent the daughter product—the atom produced by   radioactive decay—and the emitted particle.

5.   Click ‘ reset all’ and run the simulation again – what is the half life of a carbon-14 atom?

6. There are 2 other forms of beta decay: beta-plus decay, and electron capture.

A. Explain how beta plus decay is different from what we just saw in the carbon-14 decay. (Describe the difference in process and in emissions).

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B. Using the internet, see if you can find an example of beta plus decay – draw out the reaction as you have for question 4.

C. Explain how electron capture decay is different from both beta-minus decay and beta plus decay. (Describe the difference in process and in emissions).

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D. Using the internet, see if you can find an example of electron capture decay – draw out the reaction as you have for question 4.