0. NUCLEAR CHEMISTRY

1. Nuclear Radiation
Nuclear chemistry is the study of the structure of atomic nuclei and the changes they undergo.

2. The Discovery of Radioactivity
Marie Curie named the process by which materials such as uranium give off rays radioactivity; the rays and particles emitted by a radioactive source are called radiation.

3. Types of Radiation
As you may recall, isotopes are atoms of the same element that have different numbers of neutrons.
Isotopes of atoms with unstable nuclei are called radioisotopes.

4. Types of Radiation
These unstable nuclei emit radiation to attain more stable atomic configurations in a process called radioactive decay.
During radioactive decay, unstable atoms lose energy by emitting one of several types of radiation.

5. Types of Radiation
The three most common types of radiation are alpha (α), beta (β), and gamma (γ).
Alpha, Beta or Gamma? ?? ?? ??

6. Types of Radiation
Negatively charged beta particles are deflected toward the positively charged plate. ?? ?? ??

7. Types of Radiation
Positively charged alpha particles are deflected toward the negatively charged plate.
Alpha particles are deflected less than beta rays because they are more massive. ?? ??

8. Types of Radiation
Gamma rays, which have no electrical charge, are not deflected. ??

9. Alpha
An alpha particle (α) has the same composition as a helium nucleus—two protons and two neutrons—and is therefore given the symbol
The charge of an alpha particle is 2+ due to the presence of the two protons.

10. Alpha
Because of their mass and charge, alpha particles are relatively slow-moving compared with other types of radiation.
Thus, alpha particles are not very penetrating—a single sheet of paper stops alpha particles.

11. Beta
A beta particle is a very-fast moving electron that has been emitted from a neutron of an unstable nucleus.
Beta particles are represented by the symbol
The zero superscript indicates the insignificant mass of an electron in comparison with the mass of a nucleus.

12. Beta The –1 subscript denotes the negative charge of the particle.
Beta radiation consists of a stream of fast-moving electrons.

13. Beta
Because beta particles are both lightweight and fast moving, they have greater penetrating power than alpha particles.
A thin metal foil is required to stop beta particles.

14. Gamma
Gamma rays are high-energy (short wavelength) electromagnetic radiation. They are denoted by the symbol .
As you can see from the symbol, both the subscript and superscript are zero.

15. Gamma
Thus, the emission of gamma rays does not change the atomic number or mass number of a nucleus.
Gamma rays almost always accompany alpha and beta radiation, as they account for most of the energy loss that occurs as a nucleus decays.

16. Types of Radiation He α β e γ 4 +2 -1
Name Symbol Formula Mass Charge Description 4
helium nuclei He 4 +2
alpha α 2
high speed electrons β e
beta -1 -1
high energy radiation γ
gamma

17. Nuclear Stability
Radioactive nuclei undergo decay in order to gain stability.
All elements with atomic numbers greater than 83 are radioactive.

18. Balancing a Nuclear Equation
Nuclear equations are used to show nuclear transformations.  Balanced nuclear equations require that both the atomic number and the mass number must be balanced.

19. X X Balancing a Nuclear Equation A A Z Z Mass number Element symbol
Atomic number
Element symbol

20. beta gamma particle ray
Anatomy of a Decay Equation
In the early solar system, I-129 underwent beta decay to produce Xe The balanced decay equation is represented:
beta gamma particle ray
sum of mass numbers must be equal
129
129
I → Xe e + γ 53 54 -1
reaction arrow
reactants
products
sum of atomic numbers must be equal
NO SUBTRACTION

21. Anatomy of a Decay Equation
When writing a sentence as a decay equation “bombard” means the decay particle is on the reactants (left) side.
While “decay” means the decay particle is on the products (right) side.
alpha bombardment: X + He → Y
beta decay: X → Y + e
4 2
0 -1

22. Anatomy of a Decay Equation
Gamma rays are associated with most decay events, but sometimes are not explicitly included in the equation, since they do not affect mass or charge.
However it is important to remember that the ENERGY associated with decay is primarily in the form of a gamma rays.

23. Balancing a Nuclear Equation
When beryllium-9 is bombarded with alpha particles (helium nuclei), a neutron is produced.  The balanced nuclear reaction is given as: 9 4 1
Be He → n +
??? 4 2

24. Balancing a Nuclear Equation9 4 1
Be He → n +
??? 4 2
On the reactant side, the mass numbers equal (9 + 4) = 13.
On the product side, the mass number equals 1.
The product side needs an additional 12 for the mass number.

25. Balancing a Nuclear Equation9 4 1
Be He → n +
??? 4 2
On the reactant side, the atomic numbers equal (4 + 2) = 6.
On the product side, the atomic number equals 0.
The product side needs an additional 6 for the atomic number.

26. Balancing a Nuclear Equation9 4 1 12
Be He → n +
??? 4 2 6
The atomic number (the number on the bottom) determines the identity of the element.

27. Balancing a Nuclear Equation9 4 1 12
Be He → n + C 4 2 6
The element with an atomic number of 6 is carbon.

28. Balancing a Nuclear Equation
When nitrogen-14 is bombarded with a neutron, a proton is produced. The balanced nuclear equation can be written as:
N n → p + 14 7 1
???

29. Balancing a Nuclear Equation
N n → p + 14 7 1
???
On the reactant side, the mass numbers equal (14 + 1) = 15.
On the product side, the mass number equals 1.
The product side needs an additional 14 for the mass number.

30. Balancing a Nuclear Equation
N n → p + 14 7 1
???
On the reactant side, the atomic numbers equal (7 + 0) = 7.
On the product side, the atomic number equals 1.
The product side needs an additional 6 for the atomic number.

31. Balancing a Nuclear Equation14 1 1 14
N n → p +
??? 7 1 6
The atomic number (the number on the bottom) determines the identity of the element.

32. Balancing a Nuclear Equation14 1 1 14
N n → p + C 7 1 6
The element with an atomic number of 6 is carbon.

33. Balancing a Nuclear Equation
226
230 4
Th → He
??? Ra 90 88 2
Balance the nuclear reaction above.

34. Balancing a Nuclear Equation
230
234 4
U → He
??? Th 92 90 2
Balance the nuclear reaction above.

35. Balancing a Nuclear Equation50 50
Co → e
??? Ni 27 28 -1
Balance the nuclear reaction above.

36. Balancing a Nuclear Equation
Sometimes you must use atoms other than those on the periodic table to balance nuclear reactions.

37. Balancing a Nuclear Equation

38. Question
What element is formed when undergoes beta decay? Give the atomic number and mass number of the element.

39. Question
Write a balanced nuclear equation for the alpha decay of the following radioisotope.

40. Question
Uranium-238 is bombarded with a neutron. One product forms along with gamma radiation. Write the balanced nuclear equation.
U n → U γ
238 92 1
239

41. Question
Nitrogen-14 is bombarded with deuterium (hydrogen-2). One product forms along with an alpha particle. Write the balanced nuclear equation.
N H → C He 14 7 2 1 12 6 4

42. Radioactive Decay Rates
Radioactive decay rates are measured in half-lives.
A half-life is the time required for one- half of a radioisotope’s nuclei to decay into its products.

43. Radioactive Decay Rates
For example, the half-life of the radioisotope strontium-90 is 29 years.
If you had 10.0 g of strontium-90 today, 29 years from now you would have 5.0 g left.
The decay continues until negligible strontium-90 remains.

44. Radioactive Decay Rates
The graph shows the percent of a stontium- 90 sample remaining over a period of four half-lives.
With the passing of each half-life, half of the strontium-90 sample decays.

45. Calculating Amount of Remaining Isotope
total time
time of 1 half-life
number of half-lives n
mf = mi ∙ (½)
final mass
initial mass

46. Calculating Amount of Remaining Isotope
Iron-59 is used in medicine to diagnose blood circulation disorders.
The half-life of iron-59 is 44.5 days.
How much of a mg sample will remain after days?
( mg)

47. Question
Cobalt-60 has a half-life of 5.27 years. How much of a 10.0 g sample will remain after years?
(0.625 g)

48. Question
Carbon-14 has a half-life of 5730 years. If 125 grams remain after 5730 years, what was the mass of the initial sample??
(250 g)

49. Question
A 40 g sample of Ba-126 decays to 10 g in 200 minutes. What is the half-life (in minutes) of Ba-126?
(100 minutes)

50. Nuclear Fission
Heavy atoms (mass number > 60) tend to break into smaller atoms, thereby increasing their stability.
Using a neutron to split a nucleus into fragments is called nuclear fission.
Nuclear fission releases a large amount of energy and several neutrons.

51. Nuclear Fission
Since neutrons are products, one fission reaction can lead to more fission reactions, a process called a chain reaction.
A chain reaction can occur only if the starting material has enough mass to sustain a chain reaction; this amount is called critical mass.

52. Nuclear Fusion
The combining of atomic nuclei is called nuclear fusion.
For example, nuclear fusion occurs within the Sun, where hydrogen atoms fuse to form helium atoms.

53. Nuclear Fusion
Fusion reactions can release very large amounts of energy but require extremely high temperatures. For this reason, they are also called thermonuclear reactions.

54. Comparing Nuclear Reactions
Type
Description
Applications
Decay
Happens spontaneously, independent of temperature
Medicine, Radio-dating
Fission
Because of chain reactions, creates more energy than decay
Nuclear Energy, First atomic bombs
Fusion
Requires a massive amount of heat and pressure, beyond what can be created (so far) on Earth.
Happens in the cores of stars. Thermonuclear weapons, Holy Grail of sustainable energy

55. Question
What is the difference between nuclear fusion and nuclear fission?
Nuclear fusion is the combining of nuclei to form a single nucleus. Nuclear fission is the splitting of a nucleus into fragments.

56. Applications and Effects of Nuclear Reactions
Geiger counters, scintillation counters, and film badges are devices used to detect and measure radiation.

57. Applications and Effects of Nuclear Reactions

58. Applications of Nuclear Reactions
Geiger counters use ionizing radiation, which produces an electric current in the counter, to rate the strength of the radiation on a scale.

59. Applications of Nuclear Reactions
Film badges are often used to monitor the approximate radiation exposure of people working with radioactive materials.

60. Applications of Nuclear Reactions
Scintillation counters measure ionizing radiation.

61. Applications of Nuclear Reactions
With proper safety procedures, radiation can be useful in industry, in scientific experiments, and in medical procedures.

62. Applications of Nuclear Reactions
Nuclear power plants use the process of nuclear fission to produce heat in nuclear reactors.
The heat is used to generate steam, which is then used to drive turbines that produce electricity.

63. Nuclear Reactors

64. Applications of Nuclear Reactions
A radiotracer is a radioisotope that emits non-ionizing radiation and is used to signal the presence of an element or of a specific substance.
Radiotracers are used to detect diseases and to analyze complex chemical reactions.

65. Applications of Nuclear Reactions

66. Applications of Nuclear Reactions
Ionizing radiation has many uses. An X-ray is ionizing radiation, and ionizing radiation can be used in medicine to kill cancerous cells.

67. Applications of Nuclear Reactions
Most medical devices require sterilization after they are packaged, and another trend has been the move to sterilization by gamma radiation as opposed to other methods such as ethylene oxide gas. Advantages of gamma irradiation include speed, cost- effectiveness, and the elimination of the need for special packaging.

68. Applications of Nuclear Reactions
Chemical reaction rates are greatly affected by changes in temperature, pressure, and concentration, and by the presence of a catalyst.
In contrast, nuclear reaction rates remain constant regardless of such changes.
In fact, the half-life of any particular radioisotope is constant.

69. Applications of Nuclear Reactions
Because of this, radioisotopes, especially carbon-14, can be used to determine the age of an object.
The process of determining the age of an object by measuring the amount of a certain radioisotope remaining in that object is called radiochemical dating.

70. Radiochemical Dating

71. Effects of Nuclear Reactions
Any exposure to radiation can damage living cells.
Gamma rays are very dangerous because they penetrate tissues and produce unstable and reactive molecules, which can then disrupt the normal functioning of cells.

72. Effects of Nuclear Reactions
The amount of radiation the body absorbs (a dose) is measured in units called rads and rems.
Everyone is exposed to radiation, on average 100–300 millirems per year A dose exceeding 500 rem can be fatal.