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Nuclear Decay Investigation Mark as Favorite (13 Favorites)

ACTIVITY in Radiation, Isotopes, Alpha/Beta/Gamma Decay, Radioactive Isotopes. Last updated December 21, 2022.


In this activity, students will explore different types of radioactive decay using a decay chain. Through modeling and analyzing a decay chain, students will familiarize themselves with different isotopes, and begin to understand how decay affects the nucleus of an atom.

Grade Level

High School

NGSS Alignment

This activity will help prepare your students to meet the performance expectations in the following standards:

  • 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.
  • Scientific and Engineering Practices:
    • Using Mathematics and Computational Thinking
    • Developing and Using Models
    • Obtaining, Evaluating, and Communicating Information


By the end of this activity, students should be able to:

  • Explain how alpha and beta decay affect the nucleus of an atom.

Chemistry Topics

This lesson supports students’ understanding of:

  • Radioactive Decay
  • Alpha, Beta, and Gamma particles
  • Radiation
  • Atomic Number
  • Isotopes


Teacher Preparation: 10 minutes
Lesson: 60 minutes


  • Laptops/iPads with internet
  • Periodic Table


  • No safety precautions need to be observed for this activity.

Teacher Notes

  • Nuclear decay chains show the sequence of radioactive decay. They indicate what radioactive particles are given off during decay and what isotopes are formed in the process. The decay chain continues until no unstable isotopes are formed. The last isotope in the decay chain has a stable nucleus.
  • A decay chain activity is a good addition to a lesson on radioactive decay because decay chains help students conceptualize the path that an unstable atom takes to become stable and also shows the radiation that is emitted throughout the process. This also helps students apply the law of conservation of mass.
  • Students will refer to Lead-215’s decay chain for use in the activity. It might be helpful for teachers to familiarize themselves with it beforehand.
  • Before students start the activity, teachers could spend a few minutes reminding students where to find the atomic number for an element using the periodic table and where to write it in an isotope symbol.
  • Using the ACS Chemistry Basics video, What are Isotopes?, along with the corresponding AACT video questions, might also be helpful. As well as discussing/reminding students about the relationship between number of protons and charge of the nucleus.
  • To differentiate the activity, challenge higher-level students to find a decay chain using the same website that has a different type of decay than Lead-215. Students can also identify how a different type of decay affects the parent isotope. Teachers can guide lower-level students by drawing the first step in the decay chain and counting the change in the mass and the atomic number together.

For the Student


You will draw the decay paths for various isotopes of different elements and look for:

  • A pattern of how they decay.
  • What form(s) of decay they take.
  • How the form(s) of decay affect the overall nucleus.


Radioactive decay is a process in which an unstable atom falls apart to form a more stable atom. Atoms with too many protons or neutrons in the nucleus undergo radioactive decay to become stable. During this process, radiation is released. Common types of radiation released during decay are alpha radiation, beta radiation, and gamma radiation.


You will draw and analyze the decay path (also referred to as a decay chain) of Lead-215.

The image below shows an example of what a portion of the decay chain looks like:

Decay Path and Analysis

  1. Using this source (https://periodictable.com/Isotopes/082.215/index.html), draw the decay path for Lead-215 in the space below.
    1. Make sure to include the radiation symbols between the arrows in your decay path drawing.
    2. Use your periodic table to write down the atomic number below the mass.
  2. Use the decay path in question one as a reference. Describe how each symbol changed the nucleus from its previous form (parent isotope) to its form afterwards (daughter isotope). Write a few sentences about what you learned during the simulation using the prompts below.
    1. How did giving off an α particle change the mass?
      1. The mass stayed the same / increased / decreased by _____.
      2. The atomic number stayed the same / increased / decreased by _____.
    2. How did giving off a β- particle change the mass?
      1. The mass stayed the same / increased / decreased by _____.
      2. The atomic number stayed the same / increased / decreased by _____.
  3. What did you learn from this activity? (2-3 sentences)
  4. Look at the equations in the model. Explain what happens to the nucleus of each of the starting elements for both alpha and beta decay during the nuclear decay process. Specifically mention how the atomic mass and the charge change.
  1. Write a claim, evidence, and reasoning explaining why the decay process stops. Use your prior knowledge about nuclear chemistry and isotopes.


(What causes this?)

(Give data from your observations to back up your claim.)

(How does the data support this? Refer to scientific principles.)