1. Nuclear Chemistry: The Heart of Matter
Chemistry for Changing Times 10th edition
Hill/Kolb
Chapter 4
Nuclear Chemistry: The Heart of Matter
Daniel Fraser
University of Toledo, Toledo OH
©2004 Prentice Hall

2. Types of Radiation
Ionizing radiation – knocks electrons out of atoms or groups of atoms
Produces charged species – ions
Charged species that cause damage
Chapter 4

3. Differences Between Chemical and Nuclear Reactions
Chapter 4

4. Half-Life
Period for one-half of the original elements to undergo radioactive decay
Characteristic for each isotope
Fraction remaining =
n = number of half-lives
Chapter 4

5. Practice Problems
Chapter 4

6. Radioisotopic Dating
Use certain isotopes to estimate the age of various items
235U half-life = 4.5 billion years
Determine age of rock
3H half-life = 12.3 years
Used to date aged wines
Chapter 4

7. Chapter 4 1 April 2017 04-TB05 Title:
Table 4.5 Several Isotopes Useful in Radioactive Dating
Caption:
Isotopes commonly used to determine the age of matter. Note the range limitations for each isotope.
Notes:
Carbon-14 dating is the most commonly recognized dating procedure.
Chapter 4
Chapter 4

8. Carbon-14 Dating 99.9% 12C Produce 14C in upper atmosphere
Half-life of 5730 years
~50,000 y maximum age for dating
Chapter 4

9. Example 4.2 Half-Lives Solution Exercise 4.2A Exercise 4.2B
You obtain a new sample of cobalt-60, half-life 5.25 years, with a mass of 400 mg. How much cobalt-60 remains after years (three half-lives)?
Solution
The fraction remaining after three half-lives is 1 2n 23
2 x 2 x 2 8 =
The amount of cobalt-60 remaining is ( ) (400 mg) = 50 mg.
You have mg of freshly prepared gold-189, half-life 30 min. How much of the gold-189 sample remains after five half-lives?
Exercise 4.2A
What percentage of the original radioactivity remains after five half-lives?
Exercise 4.2B
Chapter 4

10. Example 4.3 Solution Exercise 4.3A Exercise 4.3B
You obtain a 20.0-mg sample of mercury-190, half-life 20 min. How much of the mercury-190 sample remains after 2 hr?
There are 120 min in 2 hr. There are ( ) = 6 half-lives in 2 hr. The fraction remaining
after six half-lives is
The amount of mercury-190 remaining is ( ) (20.0 mg) = mg.
Solution 1 2n 26
2 x 2 x 2 x 2 x 2 x 2 64 =
120 20
A sample of 16.0 mg of nickel-57, half-life 36.0 hr, is produced in a nuclear reactor. How much of the nickel-57 sample remains after 7.5 days?
Exercise 4.3A
Tc-99 decays to Ru-99 with a half-life of 210,000 years. Starting with 1.0 mg of Tc-99, how long will it take for 0.75 mg of Ru-99 to form?
Exercise 4.3B
Chapter 4

11. ( ) Example 4.4 Solution Exercise 4.4
A piece of fossilized wood has carbon-14 activity one-eighth that of new wood. How old is the artifact? The half-life of carbon-14 is 5730 years.
Solution
The carbon-14 has gone through three half-lives:
It is therefore about 3 x 5730 = 17,190 years old. 1 8 = 2 x
( ) 3
How old is a piece of cloth that has carbon-14 activity that of new cloth fibers? The half-life of carbon-14 is 5730 years.
Exercise 4.4 1 16
Chapter 4

12. Shroud of Turin Alleged burial shroud of Jesus Christ
Contains faint human likeness
First documented in Middle Ages
Carbon-14 dating done in 1988
Three separate labs
Shroud ~800 years old
Unlikely to be burial shroud
Chapter 4

13. Uses of Radioisotopes Tracers Agriculture Easy to detect
Different isotopes have similar chemical and physical properties
Physical, chemical, or biological processes
Agriculture
Induce heritable genetic alterations – mutations
Preservative
Destroys microorganisms with little change to taste or appearance of the food
Chapter 4

14. Nuclear Medicine Used for two purposes
Therapeutic – treat or cure disease using radiation
Diagnostic – obtain information about patient’s health
Chapter 4

15. Radiation Therapy Radiation most lethal to dividing cells
Makes some forms of cancer susceptible
Try to destroy cancer cells before too much damage to healthy cells
Direct radiation at cancer cells
Gives rise to side effects
Chapter 4

16. Diagnostic Uses Many different isotopes used
See Table 4.6
Can measure specific things
Iodine-131 to locate tumors in thyroid
Selenium-75 to look at pancreas
Gadolinium-153 to determine bone mineralization
Chapter 4

17. Imaging Positron emission tomography (PET)
Uses an isotope that emits a positron
Observe amount of radiation released
Chapter 4

18. Chapter 4 1 April 2017 04-TB06 Title:
Table 4.6 Some Radioisotopes and Their Medical Applications
Caption:
Isotopes used for diagnosis and therapy in the medical field.
Notes:
Note that most isotopes have relatively short half-lives.
Chapter 4
Chapter 4

19. Penetrating Power of Radiation
The more mass the particle has, the less penetrating it is
The faster the particle is, the more penetrating it is
Chapter 4

20. Prevent Radiation Damage
To minimize damage
Stay a distance from radioactive sources
Use shielding; need more with more penetrating forms of radiation
Chapter 4

21. Energy from Nucleus E = mc2 Lose mass, gain energy
For chemical reactions, mass changes are not measurable
For nuclear reactions, mass changes may be measurable
Chapter 4

22. Binding Energy Holds protons and neutrons together in the nucleus
The higher the binding energy, the more stable the element
Chapter 4

23. Nuclear Fission “Splitting the atom”
Break a large nucleus into smaller nuclei
Chapter 4

24. Nuclear Chain Reaction
Neutrons from one fission event split further atoms
Only certain isotopes, fissile isotopes, undergo nuclear chain reactions
Chapter 4

25. Manhattan Project How to sustain the nuclear reaction?
How to enrich uranium to >90% 235U?
Only 0.7% natural abundance
How to make 239Pu (another fissile isotope)?
How to make a nuclear fission bomb?
Chapter 4

26. Radioactive Fallout
Nuclear bomb detonated; radioactive materials may rain down miles away and days later
Some may be unreacted U or Pu
Radioactive isotopes produced during the explosion
Chapter 4

27. Nuclear Power Plants Provide ~20% U.S. electricity
France >70%
Slow controlled release of energy
Need 2.5–3.5% 235U
Problem with disposal of radioactive waste
Chapter 4

28. Nuclear Fusion Reaction takes smaller nuclei and builds larger ones
Also called thermonuclear reactions
Releases tremendous amounts of energy
1 g of H would release same as 20 tons of coal
Chapter 4

29. End of Chapter 4
Chapter 4

30. Radioisotopes Radioactive decay – Many isotopes are unstable
Nuclei that undergo radioactive decay
May produce one or more types of radiation
Chapter 4

31. Natural Radioactivity
Background radiation
What occurs from natural sources
>80% of radioactivity exposure
Chapter 4

32. Nuclear Equations Elements may change in nuclear reactions
Total mass and sum of atomic numbers must be the same
MUST specify isotope
Chapter 4

33. Alpha Decay Nucleus loses  particle
Mass decreases by 4 and atomic number decreases by 2
Chapter 4

34. Beta Decay Nucleus loses  particle
No change in mass but atomic number increases
Chapter 4

35. Positron Emission Loses a positron
Equal mass but opposite charge of an electron
Decrease in atomic number and no change in mass +
Chapter 4

36. Electron Capture
Nucleus absorbs an electron and then releases an X-ray
Mass number stays the same and atomic number decreases
Chapter 4

37. Gamma Radiation Release of high-energy photon
Typically occurs after another radioactive decay
No change in mass number or atomic number
Chapter 4

38. Artificial Transmutation
Transmutation changes one element into another
Middle Ages: change lead to gold
In 1919 Rutherford established protons as fundamental particles
Basic building blocks of nuclei
Chapter 4

39. Example 4.1 Balancing Nuclear Equations
Write balanced nuclear equations for each of the following processes. In each case, indicate what new element is formed.
a. Plutonium-239 emits an alpha particle when it decays.
b. Protactinium-234 undergoes beta decay.
c. Carbon-11 emits a positron when it decays.
d. Carbon-11 undergoes electron capture.
Solution
a. We start by writing the symbol for plutonium-239 and a partial equation showing that
one of the products is an alpha particle (helium nucleus):
239 94 Pu 4 2
He + ?
Mass and charge are conserved. The new element must have a mass of 239 – 4 = 235
and a charge of 94 – 2 = 92. The nuclear charge (atomic number) of 92 identifies the
element as uranium (U):
He +
235 92 U
Chapter 4

40. Example 4.1 Balancing Nuclear Equations (cont.)
b. Write the symbol for protactinium-234 and a partial equation showing that one of the
products is a beta particle (electron):
234 91 Pa –1
e + ?
The new element still has a mass number of 234. It must have a nuclear charge of 92
in order for the total charge to be the same on each side of the equation. The nuclear
charge identifies the new atom as another isotope of uranium (U):
234 91 Pr –1
e + 92 U
c. Write the symbol for carbon-11 and a partial equation showing that one of the
products is a positron: 11 6 C +1
e + ?
To balance the equation, a particle with a mass number of 11 and an atomic number
of 5 (B) is required:
e + 5 B
Chapter 4

41. Example 4.1 Balancing Nuclear Equations (cont.)11 6 C –1 e
d. We write the symbol for carbon-11 and a partial equation showing it capturing
an electron: + ? 11 6 C –1 e 5 B
To balance the equation, the product must have a mass number of 11 and an atomic
number of 5 (B): +
As mentioned in the text, positron emission and electron capture result in identical
changes in atomic number, and therefore the identical elements are formed! Also, as
parts (c) and (d) illustrate, C-11 (and certain other nuclei) can undergo several different
types of radioactive decay processes.
Write balanced nuclear equations for each of the following processes. In each case, indicate what new element is formed.
Exercise 4.1
a. Radium-226 decays by alpha emission.
b. Sodium-24 undergoes beta decay.
c. Gold-188 decays by positron emission.
d. Argon-37 undergoes electron capture.
Chapter 4

42. Example 4.5 Solution Exercise 4.5
When potassium-39 is bombarded with neutrons, chlorine-36 is produced. What other particle is emitted?
Cl + ? 36 17 1 n 39 19
K +
Solution
Write a balanced nuclear equation. To balance the equation, we need four mass units
and two charge units (that is, a particle with a nucleon number of 4 and an atomic
number of 2). That’s an alpha particle.
Cl + 36 17 1 n 39 19
K + He 4 2
Technetium-97 is produced by bombarding molybdenum-96 with a deuteron (hydrogen-2 nucleus). What other particle is emitted?
Exercise 4.5
Tc + ? 97 43 2 1 H 96 42
Mo +
Chapter 4

43. Example 4.6 Solution Exercise 4.6
One of the isotopes used for PET scans is oxygen-15, a positron emitter. What new element is formed when oxygen-15 decays?
Solution
First write the nuclear equation +1
e + ? 15 8 O
The nucleon number does not change, but the atomic number becomes 8 – 1, or 7; and so
the new product is nitrogen-15:
e + 7 N
Phosphorus-30 is a positron-emitting radioisotope suitable for use in PET scans. What new element is formed when phosphorus-30 decays?
Exercise 4.6
Chapter 4

44. 1 April 2017
04-01
Title:
Distribution Chart for Radiation Exposure
Caption:
Pie chart showing the sources of radiation exposure.
Notes:
Percent exposure from various radiation sources.
Chapter 4
Chapter 4

45. Chapter 4 1 April 2017 04-02 Title: Alpha and Beta Emission Caption:
Nuclei undergoing alpha and beta emission.
Notes:
Radioactive decay is a balanced reaction in terms of mass numbers and charges.
Chapter 4
Chapter 4

46. 1 April 2017
04-03
Title:
Positron Emission and Electron Capture
Caption:
Nuclei undergoing positron emission and electron capture.
Notes:
Radioactive decay is a balanced reaction in terms of mass numbers and charges.
Chapter 4
Chapter 4

47. Chapter 4 1 April 2017 04-04 Title: Tritium Decay Caption:
Graph showing the decay of tritium with a half-life of 12.3 years.
Notes:
Assume that radioactivity is essentially gone after 10 half-lives.
Chapter 4
Chapter 4

48. Chapter 4 1 April 2017 04-08 Title: Analogy for Radiation Penetration
Caption:
Alpha particles stop more quickly than beta particles. Gamma radiation is the hardest to stop.
Notes:
Alpha particles are highly dangerous inside the body.
Chapter 4
Chapter 4

49. Chapter 4 1 April 2017 04-09 Title: Penetrating Power of Radiation
Caption:
The relative penetrating power of alpha, beta, and gamma radiation.
Notes:
Like X-rays, gamma rays can pass through the body.
Chapter 4
Chapter 4

50. Chapter 4 1 April 2017 04-10 Title: Nuclear Binding Energy for Helium
Caption:
The difference in mass between the individual particles in the helium nucleus and its actual mass. The missing mass is converted into the nuclear binding energy.
Notes:
The missing mass is known as the mass defect.
Chapter 4
Chapter 4

51. Chapter 4 1 April 2017 04-11 Title: Nuclear Binding Energy Caption:
Graph showing that nuclear binding energy reaches a maximum at iron.
Notes:
Note that very low mass elements to the left of iron undergo fusion to gain nuclear stability while those to the right of iron undergo fission.
Chapter 4
Chapter 4

52. Chapter 4 1 April 2017 04-12 Title: Nuclear Fission Caption:
The fission of an atom of uranium-235.
Notes:
The fission of a particular isotope does not always produce the same products. Not all atoms undergo fission.
Chapter 4
Chapter 4

53. Chapter 4 1 April 2017 04-13 Title: Nuclear Chain Reaction Caption:
The process by which a chain reaction develops when uranium-235 undergoes fission. Note the different fission products.
Notes:
Uncontrolled chain reactions lead to powerful explosions.
Chapter 4
Chapter 4

54. Chapter 4 1 April 2017 04-17-01UN Title: End-of-Chapter Problem 63
Caption:
Fission reaction for end-of-chapter Problem 63.
Notes:
problem image
Chapter 4
Chapter 4

55. Chapter 4 1 April 2017 04-TB01 Title:
Table 4.1 Common Types of Radiation in Nuclear Reactions
Caption:
Properties of alpha, beta, and gamma radiation.
Notes:
the three major types of radiation
Chapter 4
Chapter 4

56. Chapter 4 1 April 2017 04-TB02 Title:
Table 4.2 Radioactive Decay and Nuclear Change
Caption:
Changes in atomic and mass number during radioactive decay processes.
Notes:
Atomic and mass numbers are balanced.
Chapter 4
Chapter 4

57. Chapter 4 1 April 2017 04-TB03 Title:
Table 4.3 Some Differences Between Chemical Reactions and Nuclear Reactions
Caption:
Comparison of chemical and nuclear reactions.
Notes:
Nuclear reactions may produce different daughter elements, while chemical reactions conserve the starting elements.
Chapter 4
Chapter 4

58. Chapter 4 1 April 2017 04-TB04 Title:
Table 4.4 Nuclear Symbols for Subatomic Particles
Caption:
Symbols used to represent particles in nuclear reaction equations.
Notes:
balancing nuclear reactions
Chapter 4
Chapter 4