Balancing Nuclear Equations

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Students will be able to write balanced nuclear equations for different types of nuclear decay.

Big Idea

Nuclear decay can be represented using balanced nuclear equations.


Unit Overview: This unit, called Passion, Power, and Peril, is an inter-disciplinary unit between two classes—English and Chemistry. In Chemistry class, students will learn about nuclear chemistry, but they will also research a specific aspect of the nuclear power industry. They will use this research in three ways. First, they will write a one-page paper for a Chemistry grade that explains how nuclear chemistry connects to the research topic. Second, students will write an informative/explanatory research paper that answers your research question by showing the complexity of the issue for an English grade. Finally, students will use their research and writing to create a piece of artwork for a multimedia art display designed to challenge the audience with weighing the costs and benefits of nuclear technology.

In this process we would like students to consider the following questions: How does society evaluate costs and benefits of a technology?  What are the costs and benefits of nuclear power plants? 

Lesson Overview: In this lesson students will be able to write balanced nuclear equations for different types of nuclear decay.

This lesson aligns to the NGSS Disciplinary Core Idea of HS-PS1-8. Develop models to illustrate the changes in the composition of the nucleus of the atom and the energy released during the processes of fission, fusion, and radioactive decay because students use nuclear equations to model changes in the composition of the nucleus.

For this reason it also aligns to the NGSS Practice of the Scientist of Developing and using models.

It aligns to the NGSS Crosscutting Concept of Energy and Matter by helping students learn that In nuclear processes, atoms are not conserved, but the total number of protons plus neutrons is conserved.

In terms of prior knowledge or skills, students should have a basic understanding of the different types of decay as found in this lesson.

There are no special materials needed for this lesson.

Do Now/Activator

10 minutes

Do Now: To start class I ask students to review with a partner the different types of nuclear decay. They can use their notes.

I reason that this is a good way to start class because it will help them access prior knowledge, as this was a topic that they recently studied and modeled.

Activator: I randomly select students to answer the following questions about nuclear decay:

What is emitted in (alpha, beta, gamma, positron emission)?

What are the symbols for (alpha particles, beta particles, gamma radiation, positrons)?

What gets converted in (alpha decay, beta decay, gamma decay, positron emission)?

Most students have these student decay notes already, so this is a low stakes way for students to get back into nuclear chemistry after their February vacation.


Mini-lesson and Guided Practice

15 minutes

Mini-lesson: I now show how to use this information to complete nuclear equations. This video gives an overview of the material that I present.

This instructional choice reflects my desire to get students working and grappling with these problems as soon as possible. The day after a vacation is not the day for me to give a long lecture. Rather, a more student-friendly approach is to give them enough information to get started, and then let them try to figure it out.

Guided Practice: To facilitate this process, I ask students to do one of each type of problem in Nuclear chemistry equations I. I found these practice problems on this website. Students work alone during this portion of the lesson because I want them to assess their own comprehension. they will have a chance to get help, but first I want them to discover what exactly they need help on.

I chose this particular approach so that students would either get to practicing, or they would realize they did not understand the material and they would then be more inclined to ask questions. Once this happens, I know they have given the material some thought and they are more ready to listen to instruction.

As it turns out, about half the students understood the problems right from the beginning, while the other half needed re-teaching. For the second group, I simply restated what I had already stated, and for some reason it made more sense the second time around—probably because they had started to think about the problems through grappling with them.


25 minutes

Student Activity: Once I feel good that all students know how to work on these problems, I release them to work on additional practice problems, namely the ones found in Nuclear chemistry equations practice sheet II.

I want students doing this work because I know from experience that if students can practice the work they understand they will have a better chance of being able to replicate their understanding in the future.

While students are working I walk around the room offering words of encouragement

Catch and Release Opportunities: At some point it feels like too many students are asking me if their work is correct, and I get a bit flustered. I stop class and reiterate the lesson, with an emphasis this time on how students can check their work. Some things they need to watch out for are making sure they have the right particle, with the right sign. They need to be sure to change the element for all the decay types except gamma. Finally, the math needs to add up. These are things that students can check themselves. I explain that we will check in as a whole class during debrief.

Stopping class to discuss this is important because I want students to gain confidence and not rely on me at the expense of developing this confidence.



10 minutes

To wrap this lesson up I invite a student to present their work and defend their answers as shown in this debrief video. Here are the answers he presents. While I am pleased with the student’s ability to show balanced nuclear equations, I wished in retrospect that I had asked students to take their thinking farther by asking them to link the conversions that are happening in the nucleus to the equation. For example, radium becomes actinium in beta decay because a neutron becomes a proton and that increases the atomic number by one.

This student work was typical of what students produced. Interestingly, many students felt completely bewildered at the start of this class and them marveled at how easy it was in retrospect.