Transcript ELECTROCHEMISTRY AND ITS APPLICATIONS GENERAL …

Introduction to Nuclear
Chemistry
Chapter 19
I. Study of Nuclear Reactions
Nuclear Reactions vs. Chemical Reactions
Define “ Chemical Reaction”?
Define “Nuclear Reaction”
Reaction involving spontaneous emission of
radiation by an unstable nuclei to a more
stable nuclei of a different element.
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226
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Ra  alpha particle 
Ra  alpha particle 
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Rn
222
86
Rn
Involves changes within nucleus.
Atoms of each element do not balance.
Spontaneous change of a radioisotope.
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Ra  alpha particle 
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Rn
II. Types of Nuclear Radiation
**Responsible for properties of top three!!
Example Nuclear Reactions:
Ra  He 
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U  e 
239
93
226
88
239
92
4
2
0
-1
Th * 
230
90
 
0
0
Rn
Np
230
90
Th
Rules For Balancing Nuclear Reactions:
1. The sum of the mass numbers of the
reactants must equal the sum of the mass
number of the products.
*Total # nucleons remain the same.
2. The sum of the atomic numbers of the
reactants must equal the sum of the mass
number of the products.
* Electrical charge remains the same.
What kind of radiation is produced in the
following nuclear reaction?
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Rn 
Po  ?
218
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222
86
Rn 
Po  ?
218
84
III. Radioactive Decay Rates
Follows First Order Kinetics
Commonly described by “half-life”.
t1/2
“The time required for half the radioactive
atoms in a sample to undergo decay.”
ln
[ A]t
[ A]o
 kt
Derived From Integrated Rate Law:
[ A]t
ln
 - kt
[ A]o
t
1/ 2
0.693

k
Examples of Half-Lives
Iodine-131 (t1/2 = 8 days)
Example Problem:
The value of t1/2 for I-131 is 8 days.
How many I-131 atoms will remain after
24 days in a sample originally containing
6.4 x 1016 I-131 atoms?