Physics Core/AP 1 and 2

Homework

# Physics 30: 1-7 Racioactive Decay Processes

## Homework

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.
• # HERE

### Key Equations

PrincipleEquationVariables
Nuclear Sizes A: Number of nucleons (protons + neutrons)
Disintegration Energy MP: mass of parent particle
MD: mass of daughter particle
ma: mass of alpha particle
Alpha Decay N: parent particle
N': daughter particle
He: alpha particle
Beta Decay N: parent particle
N': daughter particle
e-: electron
ν: neutrino
Positron Decay N: parent particle
N': daughter particle
e+: positron
ν: neutrino
Electron capture N: parent particle
N': daughter particle
e-: electron
ν: neutrino
Gamma Decay N*: excieted parent particle
N: normal particle
γ: gamma ray photon<

### Web Lecture

Read the following weblecture before chat: Nuclear Decay

### Study Activity

Use the Types of Radiation virtual general chemistry lab at the University of Colorado site to simulate radioactive experiments. Read the lab manual (PDF), then follow its instructions to determine from the effective types of shielding which kinds of radiation each material puts out.

### 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 12 labs (honors course) or 18 labs (AP students). 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!