Nuclear Chemistry
Chapter 16 Tech Prep
Chapter 25 College Prep
Chapter 18 Honors
Key Terms
• Protons • Neutrons• Quarks• Nucleons *• Atomic Number• Mass Number• Isotopes• Nuclide **(honors only)
• Thermodynamic Stability*
• Kinetic Stability *• Radioactive Decay• Alpha Particles • Beta Particles• Gamma Particles• Zone of Stability *
Indicator C-2.5Compare alpha, beta, and gamma radiation in
terms of mass, charge, penetrating power, and the release of these particles from the nucleus.
• Radioactive nuclei that undergo decomposition falls into two categories: – change in mass number of the decaying nucleus – and those that do not change the mass number.
Alpha Radiation
• Mass number changes
• helium nuclei from a radioactive source; 2 protons and 2 neutrons; double positive charge.
• Common for heavy nuclides
• α-particle, __He
• 2 α-particle producers: U-238 and Th-230
Beta Radiation
• Mass number remains constant
• β particles (electron) , __e
• fast moving electrons formed from the decomposition of a neutron, negative charge.
• Th-234 and I-131 are beta producers.
• Neutron changes to a proton.
Gamma Radiation
• γ high-energy electromagnetic radiation given off by a radioisotope, no charge, no mass.
• Frequently accompanies nuclear decays and particle reactions
• Example: α-particle of U-238 (see page 880).
Penetrating Power
• Alpha
• Beta
• Gamma
Penetrating Power
• Alpha
• Beta
• Gamma
Low (0.05 mm) body tissue;
shielding – paper, clothing
Moderate (4mm) body tissue;
Shielding – metal foil
Very high – penetrates body easily; shielding – lead, concrete
(incomplete)
Indicator C-2.4
• Compare the nuclear reactions of fission and fusion to chemical reactions (including the parts of the atom involved and the relative amounts of energy released).
• What is fission and fusion?
Fission
• splitting of nuclei of certain isotopes into smaller fragments with similar mass numbers. Ex. U-235 and Pu-239
• Fission is used in nuclear reactor to produce energy.• It has to be controlled in the reactor. Controlling the
reaction involves 2 steps:• 1. Neutron moderation – reduces the speed of
neutrons.• 2. Neutron absorption – decreases the # of slow
moving neutrons.
Fusion
• (thermonuclear rxn.) – combining nuclei to produce a more stable nucleus of greater mass.
• Solar fusion hydrogen (protons) nuclei fuse to make helium nuclei.
• Nuclear Fusion occurs at extremely high temperature.
EQ - How does the nuclear reactions of fission and fusion compare to chemical reactions (including the parts of the atom involved and the relative amounts of energy released)?
• What parts are involved for nuclear rxns?
• What parts are involved in chemical rxns?• How does the energy released compare
between the two reactions? Hint: p. 897(honors)
C-2.6 Explain the concept of half-life, its use in determining the age of materials, and its significance to nuclear waste disposal.
What is half-life and why is it important?
Answer
• Half-life (t1/2) is the time required for one-half of the nuclei of a radioisotope sample to decay to products.
Answer
• Half-life (t1/2) is the time required for one-half of the nuclei of a radioisotope sample to decay to products.
• Carbon dating is important for determining the age of materials. All living things contain C-12 and C-14 in fixed ratios. The ratio changes when an organism dies, thus the C-14 decays to N -14. The ratio changes.
Answer
• Half-life (t1/2) is the time required for one-half of the nuclei of a radioisotope sample to decay to products.
• Carbon dating is important for determining the age of materials. All living things contain C-12 and C-14 in fixed ratios. The ratio changes when on organism dies, thus the C-14 decays to N -14. The ratio changes.
• Chemical waste may be hazardous. However, nuclear waste is even more hazardous because of the time-frame and the radiation. Only time can make nuclear waste not radioactive
Calculating amount of material remaining using half-life:
A = A0 x (1/2)n A0 = 1.0 g, n=4 [10.4/2.6=4]
A = 1.0 g x (1/2)4 A = 1.0 g x 1/16 = 0.063 g
Where
A0 is initial weight A is final weight (amount)
n is the number of half-lives. {n= Time passed ÷ half life}
• Refer to figure 18.3 (page 885).
Logical Method
n (half-life) Time Passed Amount
0 0 A0 =
BW: Half-life Problems
• #1 A patient is administered 40.0 mg of iodine-131 to assess the thyroid. How much of this nuclide will remain in the body after 40 days if the half-life is of iodine-131 is 8 days?
• #2 A patient is administered 100. mg of xenon-133 to assess the lungs. How much of this nuclide will remain in the body after 21.2 days if the half-life is of xenon-133 is 5.3 days?
Answers
• #1. A = A0 x (1/2)n n = 40/8 = 5 half-lives
A= 40.0 mg x (1/2)5 = 40.0 mg x (1/32) = 1.25 mg
• #2.A = 100. mg x (1/2) 4 n = 21.2/5.3 = 4 half-lives
A = 100. mg x (1/16) = 6.25 mg
Indicator C-2.8
Analyze a decay series chart to determine the products of successive nuclear reactions and write nuclear equations for disintegration of specified nuclides.
Refer to Table 18.3on page 886The Half-lives of Nuclides in the U-238 Decay Series.
• Answer the following questions.
• What nuclides have the following half-life?
a.) 5.0 days b.) 2.48 x 105 years
c.) 3.1 minutes d.) 1.62 x 103 years
• What is the particle produced from the above nuclides?
Answers
• What nuclides have the following half-life?
a.) bismuth-210 b.) uranium-234
c.) polonium-218 d.) radium-226
• What is the particle produced from the above nuclides?a.) beta b.) alpha
c.) alpha d.) alpha
Write the nuclear equations for disintegration of specified nuclides.
• U-238
• Ra-226
• Pb-214
• See page 880, Table 18.2 for more equations.
Detecting Radiation: Radiation emitted from isotopes and x-rays are forms of ionization radiation. It has enough energy to knock electrons off of some atoms. It cannot be detected by one’s senses.
• 3 devices used to measure the ionization radiation:
• Geiger counter - beta radiation
• Scintillation counter – all types
• Film badges – all types.
• Uses of Radiation:
• 1. Art
• 2. Crime labs
• 3. Agriculture
• 4. Diagnosing diseases
• 5. Treating diseases
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