Chapter 19 Lecture Outline

Diagnosing Appendicitis

Types of Radioactivity

1. Nuclear Particles

Name	Symbol	Symbol	Mass	Charge
Alpha	[alpha]	4He	4	+2
Beta	[beta]	1-e	0	-1
Gamma	[gamma]		0	0, radiation (light)
Neutron	n		1	0
Proton	p	1H	1	+1
Positron	+1e	+[beta]	0	+1

2. Radioactivity and reactions
1. Alpha emission: ²³⁸U -> ²³⁴Th + ⁴He

2. Beta Emission:
   1. ¹⁴C -> ¹⁴N + _-1e
      
   2. ¹n -> ¹p + _-1e (neutron -> proton + electron)

3. Positron Emission
1. ¹¹C -> ¹¹B + ₊₁e
2. ¹p -> ¹n + ₊₁e (proton -> neutron + positron)
4. Electron Capture
1. ⁴⁰K + _-1e -> ⁴⁰Ar
2. ¹p + _-1e -> ¹n (proton + electron -> neutron)

The Valley of Stability: Predicting the Type of Radioactivity

1. >83 protons are unstable
2. Magic Numbers 2, 8, 20, 28, 50, 82 are stable. If magic number of both protons and neutrons, then "double magic"
3. Even numbers of neutrons or protons are stable.
1. Both even, most stable
2. One even one odd, less stable
3. both odd, least stable
4. Belt of stability
1. If above, then decay to convert a neutron to a proton.
2. If below, then positron emission (or electron capture) to convert a proton to a neutron.

The Kinetics of Radioactive Decay and Radiometric Dating

1. Half life of radioactive isotopes
1. Radioactive decay is first order
2. First order rate law

1. For half life t_1/2 = 0.693/k
2. Amount remaining after time t
2. Uses of Radioactivity (See Mathcad)
1. ²³⁸U Dating (Age of Rock Problem from Page 907)
1. ²³⁸U -> ²⁰⁶Pb t_1/2 = 4.5*10⁹ years
2. ⁴⁰K Dating
1. ⁴⁰K + _-1e -> ⁴⁰Ar t_1/2 = 1.3x10⁹ years
3. ¹⁴C Dating
1. ¹⁴N + ¹n -> ¹⁴C + ¹H
2. ¹⁴C -> _-1e + ¹⁴N t_1/2 = 5730 years
3. Shroud of Turin (Dated at 1300 AD). Determine ¹⁴C present. What would it be if 0 AD?

The Discovery of Fission: The Atomic Bomb and Nuclear Power

Converting Mass to Energy: Mass Defect and Nuclear Binding Energy

Nuclear Fusion: The Power of the Sun

The Effects of Radiation on Life

Radioactivity In Medicine

1. Particle accelerators
1. Cyclotron (Figure 24.7, page 903)
2. Linear Accelerator (Figure24.8, page 903)
2. Induced Radioactivity (Making a radioactive isotope)
1. ²³⁰Th + ¹H --> ²²³Fr + 2 ⁴He
3. Neutron Bombardment (Use fast neutrons to prepare isotopes)
1. ⁵⁸Fe + ¹n -> ⁵⁹Fe
2. ⁵⁹Fe -> ⁵⁹Co + _-1e
3. ⁵⁹Co + ¹n -> ⁶⁰Co (Used for radiation treatment of cancer)

Please send any comments, corrections, or suggestions to svanbram@science.widener.edu.

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Last Updated Friday, May 25, 2001 1:59:43 PM