chapter 28 notes, part ii
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Chapter 28 Notes, part II. Half-life Transmutation Transuranium elements. Half-life. Every radioisotope has a specific rate of decay. It is measured by its half life (t 1/2 ) ; the amount of time it takes for ½ of a sample to decay into new elements. Half-life. - PowerPoint PPT PresentationTRANSCRIPT
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Chapter 28 Notes, Chapter 28 Notes, part IIpart IIHalf-lifeHalf-life
TransmutationTransmutation
Transuranium elementsTransuranium elements
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Half-life• Every radioisotope has a
specific rate of decay.• It is measured by its half life
(t1/2); the amount of time it takes for ½ of a sample to decay into new elements.
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Half-life• Half-lives of isotopes can range
from billions of years to fractions of a second.–Uranium-238 vs. Polonium-214
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Half-Life Formula
End amt.=start amt. x ( )OREnd amt.=start amt. x ( )
12
# half lives
12
Time elapsed length of h.l.
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Problem #1• Nitrogen-15 decays to carbon-
13 with a ½ life of 10 minutes. How long is 3 half lives?
• If there is originally 2.00g of nitrogen-15, how much remains at the end of 3 half lives?
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Problem #2• Manganese-56 is a emitter
with a half life of 2.6 hours. What is the mass of manganese-56 in an original 1.00mg sample after 10.4 hours?
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Problem #3• A sample of thorium-234
undergoes decay with a half life of 25 days. If the original sample is 0.5g how much is left at the end of 50 days?
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Transmutation• Transmutation is the changing of
an atom of one element into an atom of another element.
• Radioactive decay (which we have already seen) is a natural transmutation. Many times there is a complex series of reactions that occur as an unstable isotope stabilizes, which is called a reaction series.
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Transmutation• Other transmutations occur in
the laboratory—usually done by bombarding the nucleus of an element with high speed particles in a particle accelerator.
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Transuranium Elements• All elements above the atomic
number 92 are not found in nature; they are formed in particle accelerators and nuclear reactors.