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Ch 9 - Nuclear RadiationCh 9 - Nuclear Radiation1. Nuclear Emissions
2. Nuclear Equations
3. Producing Radioactive Isotopes
4. Half-Life
5. Nuclear Fission and Fusion
6. Uses & Effects
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ReviewRemember• Protons: + charge• Neutrons: neutral • Electrons: - charge
B115 atomic symbol
atomic number number of protons
mass number number of
protons and neutrons
Nuclear SymbolsNuclear Symbols – notice mass number is on top
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1. Nuclear Emissions
• Radiation comes from the nucleus of an atom.• Unstable nucleus emits a particle or energy
alpha
beta
gamma
• non-radioactive particle = neutron n10
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Alpha Particle
Same as a helium nucleus
(He)
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2 He or
Two protons
Two neutrons
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Beta Particle
An electron emitted from the nucleus
0
e or 1
A neutron in the nucleus breaks down1 1 0
n H + e 0 1 -1
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Gamma Radiation
• Pure radiation
• Like an X-ray but comes from the nucleus
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Radiation Protection
• Shielding
alpha – paper, clothing
beta – lab coat, gloves
gamma- lead, thick concrete
• Limit time exposed
• Keep distance from source
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Radiation Protection
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2. Nuclear Equations2. Nuclear Equations
In the reactants and products
Atomic numbers must balance
and
Mass numbers must balance
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Alpha decay
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Beta decay
234Th 234Pa + 0e 90 91 1
beta particle
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Gamma radiation
No change in atomic or mass number
11B 11B + 0
5 5 0
boron atom in a
high-energy state
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Learning CheckLearning Check• To predict the product, simply remember that
the mass number and atomic number are conserved
• What is the identity of X?
e01-23992 XU
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Learning CheckLearning Check
Write the nuclear equation for the beta emitter Co-60.
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SolutionsSolutions
60Co 60Ni + 0 e
27 28 -1
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239Npe01-23992 XU
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3. Producing Radioactive Isotopes3. Producing Radioactive Isotopes
Bombardment of atoms produces radioisotopes = 60 = 60
59Co + 1n 56Mn + 4H e
27 0 25 2
= 27 = 27
cobalt neutron manganese alpha
atom radioisotope particle
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Learning Check
What radioactive isotope is produced in the following bombardment of boron?
10B + 4He ? + 1n
5 2 0
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Solution
What radioactive isotope is produced in the following bombardment of boron?
10B + 4He 13N + 1n
5 2 7 0
nitrogen
radioisotope
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4. Half-Life of a Radioisotope4. Half-Life of a RadioisotopeThe time for the radiation level to fall (decay) to one-half its initial value
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Examples of Half-Life
Isotope Half life
C-15 2.4 sec
Ra-224 3.6 days
Ra-223 12 days
I-125 60 days
C-14 5700 years
U-235 710 000 000 years
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Learning Check
The half life of I-123 is 13 hr. How much of a 64 mg sample of I-123 is left after 26 hours?
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Solution
t1/2 = 13 hrs
26 hours = 2 x t1/2
Amount initial = 64mg
Amount remaining = 64 mg x ½ x ½
= 16 mg
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5. Fission VS Fusion5. Fission VS Fusion
Fission
large nuclei break up
235U + 1n 139Ba + 94Kr + 3 1n +
92 0 56 36 0
Energy
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Fission of Uranium-235• Chain reaction – the reaction sustains itself
by producing more neutrons
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Nuclear FusionNuclear Fusion
Fusion
small nuclei combine
2H + 3H 4He + 1n +
1 1 2 0
Occurs in the sun and other stars
Energy
• Excessive heat can not be contained
• Attempts at “cold” fusion have FAILED.
• “Hot” fusion is difficult to contain
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Learning CheckLearning Check
Indicate if each of the following are
(1) Fission (2) fusion
A. Nucleus splits
B. Large amounts of energy released
C. Small nuclei form larger nuclei
D. Hydrogen nuclei react
Energy
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SolutionSolution
Indicate if each of the following are
(1) Fission (2) fusion
A. 1 Nucleus splits
B. 1 + 2 Large amounts of energy released
C. 2 Small nuclei form larger nuclei
D. 2 Hydrogen nuclei react
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6. Uses & Effects6. Uses & Effects• Radiation - treatment of cancer• Nuclear medicine - use of radioisotopes in diagnosis
– Tracers – small amounts of radioactive substances used as probes to study internal organs
– Nuclear imaging – medical techniques involving tracers
• Food Irradiation– Food - irradiated with g rays from 60Co or 137Cs.– Irradiated milk - shelf life of 3 mo. w/o cooling.– USDA - approved irradiation of meats and eggs
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Exposure Sources
