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Introduction to Nuclear Chemistry
Chapter 19
I. Study of Nuclear Reactions
Nuclear Reactions vs. Chemical ReactionsDefine “ Chemical Reaction”?
RnparticlealphaRa 22286
22688
Define “Nuclear Reaction”Reaction involving spontaneous emission of radiation by an unstable nuclei to a more stable nuclei of a different element.
Involves changes within nucleus.Atoms of each element do not balance.Spontaneous change of a radioisotope.
RnparticlealphaRa 22286
22688
RnparticlealphaRa 22286
22688
II. Types of Nuclear Radiation **Responsible for properties of top three!!
Example Nuclear Reactions:
RnRa 22286
42
22688 He
NpeU 23993
01-
23992
* 23090
00
23090 ThTh
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?
? 21884
22286 PoRn ? 218
8422286 PoRn
III. Radioactive Decay Rates
Follows First Order KineticsCommonly described by “half-life”.
t1/2
“The time required for half the radioactive atoms in a sample to undergo decay.”
Derived From Integrated Rate Law:
ktA
A
o
t-
][
][ln
ktoAtA
][
][ln kt
oAtA
][
][ln
kt0.693
2/1
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?