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-2.5
Compare 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
• Low (0.05 mm) body tissue;
shielding – paper, clothing
• Beta
• Gamma
• 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 C14 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 C14 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)
0
Time Passed
0
Amount
A0 =
BW: Half-life Problems
• #1 A patient is administered 40.0 mg of iodine131 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 xenon133 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 886
The 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
c.) 3.1 minutes
•
b.) 2.48 x 105 years
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
c.) polonium-218
b.) uranium-234
d.) radium-226
• What is the particle produced from the above
nuclides?
a.) beta
c.) alpha
b.) 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