Learning Exercise

Radioactive Decay Lesson

This lesson attempts to teach how radioactive decay works. A two question warm-up will be ready for students as class begins. A web demo showing radioactive decay will be given and transition into an overhead lecture on decay.
Next, a lab will model the rate of decay of radioactive isotopes using a penny model. Students will work in groups to complete the lab and then present their findings to the class on a white board.
Students will be given a short quiz on the events in the lesson which will be used for individual assessment.
Course: Nuclear Processes

Halfway down the web page is a wonderful applet depicting Radioactive Decay. see more


Sequence of Activities:

1) After bell Rings, lights go off, video plays:
Announce beginning of Nuclear Processes unit, Talk about energy briefly and
place the two-question prompt on the over head.
(questions should be generic math problems that are relevant to half life
concept e.g what is half of half of half of half of 800?)

Students: Will be attempting to solve the two items on the overhead and asking
Teacher: taking role, answering questions, reviewing answers when the students
have finished with the two questions, finally announcing the outline of the days

2) PowerPoint and Web demonstration of radioactive decay
Students: actively listening to the web demo and asking question as well as
answering them
Teacher: Making transition from the two-question prompt to the lecture, and
explaining how decay half life proceeds with time

3) Lecture on radioactive decay
(should be specific to your class's achievement level - include vocabulary and
definitions, possibly alpha, beta, and gamma radiation and even decay equations
for an advanced audience)
Students: Taking notes in composition book, asking questions.
Teacher: presenting new material, monitoring students for participation and

4) Lab instructions/ pass out group hand outs
Students: Receiving hand-out and asking lab questions if confused
Teacher: Providing instruction on the lab, asking for questions, putting
students in groups, moving seats to such that they are conducive to group work,
assigning tasks for group members.

5) Penny lab
Students: Working in groups on the penny lab
Teacher: monitoring the students, asking questions about the lab to students,
keeping them involved.

6) Group presentations

Students: Showing their graph and presenting their ideas and/or solution to an
assigned problem
Teacher: giving positive feedback, offering encouragement, using the
presentation to facilitatereview of the material.

7) Final assessment quiz (please tailor the quiz to your students - rewrite if
Students: going back to their seats, and taking the quiz
Teacher: quietly observing

Radioactive Decay Quiz
Each question is ½ point

Part 1…Instructions: fill in the blank with the best fitting term from today’s
1. The time required for one-half of a radioactive isotope to decay into its
products is _______________.

2. A series of nuclear reactions that begins with an unstable nucleus and
results in the formation of a stable nucleus is _______________.

3. A radioactive isotope is also known as an unstable ____________ atom.

4. The final decayed atom is called the stable _____________ atom.

Part 2…Instructions: Solve each question. Please show your work.
5. If a sample of radioactive isotope had half of its atoms decay in 200 years,
how long would it take for 100 atoms of the same radioactive isotope to decay to
25 atoms? Show work

6. A sample of 800 Carbon-14 atoms, a radioactive isotope, has decayed to 200
atoms over a given period of time. If each time a half-life occurs ½ of the
atoms decay, how many half-life periods have occurred?

7. What is the half life of carbon-14 if it took 17,190 years for 800 atoms to
decay to 200 atoms?

8. A Radioactive isotope has a half life of 10 seconds. How many atoms will
remain after 40 seconds of a sample of 400 atoms?

Technical Notes

Instructional Materials:
Overhead projector
Dry erase markers
White boards
Web connected classroom

Differentiated Instruction:
This lesson has been designed from the perspective of my students, including English language learners, to best suit the members of my classroom (SDAIE strategy 1). I will utilize different modes of instruction to try to reach all students in the classroom. There will be a laboratory, an individual assignment, a group assignment, a presentation, and (SDAIE strategy 4) oral as well as written instruction with this activity. The lecture incorporates an internet site that show good graphical representation of decay for my visually inclined learners. I will be careful to watch my pace and use student reaction as a guide for my pace while teaching (SDAIE strategy 10).
These strategies will benefit my entire student population and will aid them in there efforts to meet of surpass the standards addressed in the lesson.


CA- California K-12 Academic Content Standards

• Chemistry, 9-12, Nuclear Processes

• Concept 11: Nuclear processes are those in which an atomic nucleus changes, including radioactive decay of naturally occurring and human-made isotopes, nuclear fission, and nuclear fusion. As a basis for understanding this concept:

Standard f: Students know how to calculate the amount of a radioactive substance remaining after an integral number of half lives have passed.

CA- CCTC Level II Technology Standards
•Standard 16: Using Technology to Support Student Learning

Element: 16(a) Each participating teacher communicates through a variety of electronic media.
Element : 16(e) Each participating teacher uses technology in lessons to increase students’ ability to plan, locate, evaluate, select, and use information to solve problems and draw conclusions. He/she creates or makes use of learning environments that promote effective use of technology aligned with the curriculum inside the classroo

Learning Objectives

Students will be able to

1) Describe how radioactive isotopes decay with time

2) Calculate the amount of a radioactive substance remaining after an integral number of half lives have passed