Module 8
1. Module 8
1.3. Lesson 1
Module 8—Nuclear Decay, Energy, and the Standard Model of the Atom
Lesson 1—The Nucleus and Radioactive Decay
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The typical household ionizing smoke detector uses nuclear reactions to detect smoke in the air. Inside such a detector is a small amount of radioactive americium-241. During normal operation, the large nucleus of this isotope spontaneously emits alpha particles, which ionize the air molecules between two charged plates generating a constant current. When smoke particles enter the detector, they prevent the alpha particles from ionizing the air and the current drops, triggering the alarm circuit and audible noise to warn anybody nearby.
The amount of radioactive material in an ionizing smoke detector is very small. This makes it safe for prolonged household use. However, manufacturers recommend that they be replaced every 10 years because the radioactive material operating the detector will eventually be depleted. Radioactive materials, such as americium-241, naturally break down, or decay, leaving a smaller nucleus as alpha particles and gamma radiation are emitted. Why does this happen? What makes a nucleus unstable enough to break down and emit smaller particles?
In this lesson you will answer the following essential questions:
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Which components make up the nucleus of an atom and what keeps them from coming apart?
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What are alpha and beta decay?
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How is the conservation of energy and mass applied to nuclear decay?
Module 8: Lesson 1 Assignment
Your teacher-marked Module 8: Lesson 1 Assignment requires you to submit responses to the following:
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Lab—LAB 1, LAB 2, LAB 3, and LAB 4
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Reflect and Connect—RC 1, RC 2, RC 3, RC 4, RC 5, RC 6, and RC 7
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Discuss—D 3
The other questions in this lesson are not marked by the teacher; however, you should still answer these questions. The Self-Check and Try This questions are placed in this lesson to help you review important information and build key concepts that may be applied in future lessons.
After a discussion with your teacher, you must decide what to do with the questions that are not part of your assignment. For example, you may decide to submit to your teacher the responses to Try This questions that are not marked. You should record the answers to all the questions in this lesson and place those answers in your course folder.