Half Life: A Radioactive Clock

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Half Life A Radioactive Clock

• 1. Why is it important for us to know how long it
  takes for a radioactive isotope to decay?
• helps doctors to know how long a radioisotope
  used for medical diagnosis will remain
  radioactive in the body
• helps scientists know how long must nuclear
  wastes be stored
• helps archaeologists determine how old artifacts
  are

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Half Life A Radioactive Clock

• 2. What is half-life? Give some examples
• time it takes for one-half the atomis in a sample
  to decay
• C-14 has a half life of 5730 years
• Po-212 is 3 x 10-7 seconds
• U-238 is 4.5 billion years

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• 3. Is it possible to predict when a given atom
  will decay?
• No we can only say that statistically speaking, a
  certain amount of matter(not atom amounts) will
  decay over a given time

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• 4. Why is C-14 such an important isotope?
• It helps us date materials that came from living
  matter
• 5. How does C-14 allow us to do this?
• Because a small amount of carbon that is ingested
  is C-14, we are all walking around radioactive

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• We get rid of this stuff every day
• We replace it with new C-14 every day
• The ratio of C-12 to C-14 is constant over your
  lifetime
• Once you die you stop taking in C-14
• The C-14 that is in you will decay over time
• The less radioactive your body is the longer it
  has been sitting around decaying

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• 6. What has been the practical application of
  this concept in recent years?
• The study of the Ice Man discovered in France in
  1991
• Researchers found that ice man contained about
  half of the C-14 present in living creatures today

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• 7. According to the evidence, how old is ice
  man?
• Little more than half of C-14 still around
• So it is a little less than a half life of time
• About 5300 years old

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• Do Chemquandary 3
• Do Modeling Matter on Page 450 for Homework

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• 8. Can half lifes or the rate of decay for
  radioisotopes be changed by us?
• No, we do not know of anything that can change it
• 9. What does this mean when we consider
  radioactive waste storage or disposal?
• We may have to wait a long time for the material
  to have decayed enough to be safe

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• Do Building Skills 4 on page 451

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2. Radioisotopes in Medicine

• 10. What are radioisotopes used in medicine for?
• a. trace abnormalities in body function
• b. locate damaged areas
• c. irradicate abnormal growths
• 11. What are tracers?
• radioisotopes with short half lives inserted into
  the body to find out what is happening

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• 12. What are some of the properties that make
  them useful?
• a. chemically and biologically behave like
  stable isotopes
• b. certain elements collect in specific parts of
  the body
• 13. What are two ways that tracers can be
  introduced to your body?
• drinking a solution that contains the tracer or
  having the tracer injected into the bloodstream

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• 14. Describe how tracers have aided in detecting
  problems with the thyroid?
• healthy thyroid normally incorporates a certain
  amount of Iodine daily, Radioiodine is introduced
  into the bloodstream and then its movement into
  and out of the thyroid is monitored using medical
  scanners, these levels are then compared to known
  levels
• 15. How has Technetium aided in locating brain
  tumors?
• fast growing cells have a tendency to take in a
  lot of Tc, so when Tc is introduced the places
  that it accumulates are monitored

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• 16. How is P-32 used?
• used in a similar way for bone cancers
• 17. How are some cancers treated with radiation?
• the tumor is exposed to ionizing energy in hopes
  that fast growing cells are killed, invariably
  good cells are killed as well

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• Do Chemquandary 4 on page 454

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Emerging Nuclear Medicine Technologies

• 18. What great advancement in science has led to
  the evolution of nuclear medicine?
• Computer science
• 19. What two technologies has really spearheaded
  this emerging science?
• Positron emission topography
• Magnetic Resonance Imaging

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Emerging Nuclear Medicine Technologies
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PET Scans

• 20. What are PET scans based on?
• A rare form of nuclear emission called a positron
• 21. What are positrons?
• Come from nucleus, same mass as a beta(e-) but
  with a positive charge
• Composed of antimatter

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• 22. How does it work?
• Positron emitter is inserted in a sugar molecule
• Since cancers grow faster than regular cells they
  need more sugar
• They will take up the sugar molecule which can be
  detected by the PET scanner

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• 23. What happens when a positron meets an
  electron?
• Both particles are destroyed creating two gamma
  rays flying in opposite directions
• PET detects these gamma rays

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MRI

• 24. When was it developed?
• shortly after WWII
• 25. Does it involve any scalpel work?
• Nope it is non invasive
• 26. What does it rely on?
• characteristics of protons

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MRI
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• 27. Where must a patient be placed?
• In a large electromagnet
• 28. How does it work?
• It emits radio waves into the patient than
  monitors how the waves are absorbed and reemitted
• It uses all this information to build a 3D picture

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• 29. Why were people hesitant to use this
  technology originally?
• Original name was Nuclear Magnetic Resonance,
  people were afraid of the word nuclear

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• 30. What are some ways in which it is being used?
• To detect cancers
• To figure out how the brain works

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• 31. List some other uses from Table V.9

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• 32. How is radiation used in industrial
  processes?
• sterilization of medical instruments and
  materials(surgical masks, syringes, gowns...)
• destroying microorganisms and small insects in
  packaged foods

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• 33. What are irradiators and how do they work?
• they all have an irradiation chamber that
  contains pellets of Co-60, the stuff to be
  irradiated is brought in on converyer belt, the
  door to the chamber slips opens for an
  appropriate amount of time and then closes back
  up
• 34. How can meat be kept vacuum packed for years?
• without the microorganisms to digest the meat,
  there is no decay.

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Artificial Radioactivity

• 35. What is transmutation?
• conversion of one element to another
• 36. Describe the first transmutation
• He42 Al2713 --gt P3015 10n
• this was done by Marie Curies daughter Irene
  Joliot Curie

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• 37. This type of equation is called a nuclear
  equation. It is really easy to balance because
  all you have to do is make sure that the mass
  numbers and atomic number add up to the same
  number of each side. Work out the following 5
  nuclear reactions.

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• 1. 2713 Al _______ --gt 3015P 10n
• 2. 24696 Cm _____ --gt 254102No 4 10n
• 3. 59 27 ___ ______--gt 60 x ______
• 4. 9642 ____ __ __ H --gt 97 43______ 10___
• 5. 20982______ 42 _____ --gt 21284 ______
  ____ 10n

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Do Building Skills 5 and ChemQuandary 5
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Extending the Periodic Table

• 38. What are the transuranium elements?
• Elements with Z higher than 92
• 39. How many were added after 1940?
• 23
• 40. Where have they been produced?
• Nuclear reactors

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Extending the Periodic Table

• 41. Who discovered Z94 through Z103?
• An Oak Ridger-Glenn Seaborg
• How are they produced?
• Bombarding heavy nuclei with small particles
• 42. How is Americium made?
• 23994Pu 2 10 n --gt 24195Am 0 -1 e

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Glenn Seaborg and Diane Hoffman
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• 43. Why is Am so important?
• It is used in smoke detectors
• 44. How was Seaborg honored?
• Element 106 was named after him
• 45. What was the controversy with elements 104
  and 105
• Both Americans and Soviets claimed to have
  discovered t

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• Both wanted to name the elements their own way
• IUPAC(International Union of Pure and Applied
  Chemistry) decided to award 104 to the
  Americans(Rutherfordium) and 105 to the
  Soviets(Dubnium)

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• Do Making Decisions on Page 460

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• 42. How are these Transuranium elements named?
• IUPAC(International Union of Pure and Applied
  Chemistry) examine the evidence and decides who
  gets the credit and the name

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• 43. Of Z 1 through 118, which ones have yet to
  be discovered?
• 113, 115, 118
• 44. What does IUPAC call an element until a
  formal name is decided?
• An name made up of Latin prefixes
• Un 1, un1, nil 0-ununnilium (110)

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• Do Making Decisions on page 460
• Read Chemistry at Work for quiz tomorrow