What do you hope to get out of course intellectually?
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A better understanding of nuclear chemistry
A better understanding of other chemistry courses
A better understanding of general chemistry
To learn something new and interesting
To learn more about radiation
A better understanding of nuclear decay and detection
To learn more about nuclear reactions
About various models of structure of the nucleus
To learn about islands of stability and how it applies to
super heavy elements
Applications to the real world
Applications to radiation therapy
Applications to medical physics research
Discovery of Radioactivity
• Henri Becquerel’s Experiment (1896):
– Becquerel was studying phosphoresence. Due to cloudy weather
conditions he stored a photographic plate with
K2UO2(SO4)2*2H2O ore in a light tight box. Discovered that the
plate was exposed. Result was inconsistent with phosphoresence.
– Put another photographic plate in a light-tight box without the
ore and exposed it to full sunlight. The plate did not develop.
– Argued that the plate was developed due to the emanation of
“uranium rays” from the ore no the result of a long-lived
phosphoresence.
• Pierre and Marie Curie’s Conclusion (1898):
– Concluded that the “Uranium Rays” were the result of the atomic
phenomena of uranium and not the result of chemical and
physical state of uranium.
Radioactive Decay
• Recall Unimolecular Dissociation
AB +C
• Radioactive Decay is identical to Unimolecular Dissociation
XY+Z
X is the parent nucleus, Y is the Daughter nucleus, and Z is the emitted particle(s)
• Over some time interval, there is some probability for a radioactive nucleus to
spontaneously alter its composition
• How do you know X  Y?
– One measures X or Y depending on
the conditions (e.g. pure X vs.
mixture of X and Y, what is readily
detectable)
• Experimentally one finds that the rate
of change in the number of atoms, N(t), is
proportional to the number of atoms.
http://www.bcscience10.com/images/0_quiz-7.2-08.gif
First Law of Radioactivity
a is a constant of integration
When t = 0, we have N0 initial # of nuclei of the radioactive substance. Therefore,
First law of Radioactivity
Half-Life
Definition: The amount of time required for one-half of
the nuclei (in a sample) to disintegrate/decay
so
or
http://physicsgoeasy.blogspot.com/2012/01/law-ofradioactive-decay.html
Half-Life Example Problem
Calculate the time it will take for a 20.0 gram sample of
I-131 to decay to 1/100 of its original mass?
I-131
Half-Life Example Problem