Summary

• de Broglie hypothesis
• The Bohr model
• (The quantum mechanical model)
• lasers

• Written quiz Ch. 30-31



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Chapter 32

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• The nucleus
• protons
• neutrons
• isotopes
• line of stability applet
Example #1





• Radioactive decay
• alpha decay
• beta minus decay
• gamma decay
Example #2
• Δm and the energy released





• Lecture learning outcomes
  A student who masters the topics in this lecture will be able to:
• describe the constituents of the atomic nucleus and explain the meaning of isotope
• write balanced nuclear decay reactions for alpha, beta minus, or gamma decay, and identify either the parent or daughter isotope
• calculate the energy released in a nuclear decay reaction by determining the mass difference Δm in atomic mass units and multiplying the result by 931.5 MeV/c², a constant that is connected to Einstein's famous relationship, E = mc².



• Practice:
  Try these additional examples
Example #3

Example #4



• Prepare:
  Read textbook section 32-3 before the next lecture

gc6 30.q2
What isotope is represented by the X in ?
A. xenon-82
B. lead-38
C. strontium-38
D. strontium-82
Answer















gc6 30.23mod
Uranium-236 () undergoes alpha decay. What is the daughter nucleus?
A.
 
B.
 
C.
 
D.
Answer















Walker5e EYU 32.1
Consider a stable nucleus with a proton number of roughly 70. Rank the numbers N, Z, and A for this nucleus in order of increasing value. Indicate ties where appropriate.
1. Z < N = A
2. A = Z < N
3. Z < N < A
4. Z < A < N
Answer















Walker5e EYU 32.2 mod
A given nucleus can undergo alpha decay, beta decay, or gamma decay. Rank the mass numbers A of the daughter isotopes for each case. Indicate ties where appropriate.
1. A_alpha < A_beta = A_gamma
2. A_beta = A_gamma < A_alpha
3. A_gamma < A_beta < A_alpha
4. A_gamma < A_alpha = A_beta
Answer























 



D. strontium-82
The number at the lower left is the atomic number Z and identifies the isotope as strontium. The number at the upper left is the mass number A and it tells you the number of nucleons is 82.




















 



B.





















 



3. Z < N < A

For heavy nuclei the neutrons N outnumber the protons Z, and the mass number A is the sum of N and Z, so it is the largest of them all.
















 



1. A_alpha < A_beta = A_gamma
The alpha particle represents 4 nucleons, so alpha emission leaves behind a daughter nucleus with four fewer nucleons. Beta and gamma decays leave behind daughter nuclei with unchanged mass number A, hence A_beta = A_gamma. Notice that the actual mass of the daughter nucleus m_daughter = m_parent − Δm, and the value of Δm depends on both the mass of the ejected particle and the energy loss E of the nucleus, because E = mc².