Physics 30: 1-7 Radioactive Decay Processes

Homework

Reading Preparation
Key Equations
WebLecture
Study Activity
Chat Preparation Activities
Chapter Quiz
Lab Work

Reading Preparation

Text Reading: Giancoli, Physics - Principles with Applications, Chapter 30, Sections 1 to 7

Study Points

30: 1We use several symbols to characterize the nucleus of an atom.
- Atomic number Z, number of protons. Determines the element type. Hydrogen always has one proton, carbon 6, oxygen 8, uranium 92.
- Neutron number N, number of neutrons. May vary for a given element atom with atomic number Z: e.g., carbon may have 6, 7, or 8 neutrons. The forms of an element that vary by neutron number are called isotopes.
- Atomic mass number A, the total of Z + N. Since protons and neutrons are similar in mass and electrons have little mass, Z+N is close to the total mass of the electron when measured in atomic mass units.
30: 2We discussed binding energy between molecules; this section deals with the binding energy holding the nucleus together, as experimentally determined. The total nuclear binding energy of an atomic nucleus divided by A, the number protons plus neutrons, gives us the energy per nucleon. The protons are held together by the strong nuclear force, which at short distances counteracts the electrical repulsion force due to like charges on the protons. (There is a second nuclear force, the weak nuclear force, displayed in certain nuclear decay situations).
30: 3In radioactive events, nuclear particles arre rearranged with the export or absorption of energy.
30: 4Alpha (α) decay is the expulsion of a particle containing 2 protons and 2 neutrons from the nucleus. Because the proton number goes down by two, the product of α decay is an atom of a different element.
30: 5Beta (β) decay is the conversion of a neutron to a proton and the expulsion of an electron from the nucleus. The proton number goes up by one, so the product of β decay is an atom of a different element.
30: 6Gamma (γ) decay is the emission of high energy from the nucleus. The atom does not change elements.
30: 7 The total number of nucleons remains constant before and after a nuclear decay event: protons and neutrons may only convert form but not be created or destroyed.

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Key Equations

Principle	Equation	Variables
Nuclear Sizes	$r \approx (1.2 * 10^{- 15} m) (A^{\frac{1}{3}})$	A: Number of nucleons (protons + neutrons)
Disintegration Energy	$Q = M_{P} c^{2} - (M_{D} + m_{a}) c^{2}$	M_P: mass of parent particle M_D: mass of daughter particle m_a: mass of alpha particle
Alpha Decay	${}_{Z}^{A}N \to {}_{Z}^{A}_{-}^{-}_{2}^{4}{N'} + {}_{2}^{4}{He}$	N: parent particle N': daughter particle He: alpha particle
Beta Decay	${}_{Z}^{A}N \to {}_{Z}^{A}_{+}_{1}{N'} + e^{-} + ν$	N: parent particle N': daughter particle e-: electron ν: neutrino
Positron Decay	${}_{Z}^{A}N \to {}_{Z}^{A}_{-}_{1}{N'} + e^{+} + ν$	N: parent particle N': daughter particle e+: positron ν: neutrino
Electron capture	${}_{Z}^{A}N + e^{-} \to {}_{Z}^{A}_{-}_{1}{N'} + ν$	N: parent particle N': daughter particle e-: electron ν: neutrino
Gamma Decay	${}_{Z}^{A}{N^{*}} \to {}_{Z}^{A}N + γ$	N*: excited parent particle N: normal particle γ: gamma ray photon

Web Lecture

Read the following weblecture before chat: Nuclear Decay

Study Activity

Use the PhET Beta Simulation and PhET Alpha Simulation simulation to explore different decay processes.

Chat Preparation Activities

Forum question: The Moodle forum for the session will assign a specific study question for you to prepare for chat. You need to read this question and post your answer before chat starts for this session.
Mastery Exercise: The Moodle Mastery exercise for the chapter will contain sections related to our chat topic. Try to complete these before the chat starts, so that you can ask questions.

Chapter Quiz

The chapter quiz is not yet due.

Lab Work

If you want lab credit for this course, you must complete at least 18 labs; you may complete more if you are preparing for the AP exam.. One or more lab exercises are posted for each chapter as part of the homework assignment. We will be reviewing lab work at regular intervals, so do not get behind!

Lab Instructions: Challenge Lab: Geiger Counter (Two Week Lab)

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Physics

Chapter 30: 1-7 Assignment