Chemistry Matter and Change

2. Nuclear Chemistry
Section 24.1 Nuclear Radiation
Section 24.2 Radioactive Decay
Section 24.3 Nuclear Reactions
Section 24.4 Applications and
Effects of Nuclear
Reactions
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3. Section 24.1 Nuclear Radiation
• Summarize the events
that led to understanding
radiation.
nucleus: the extremely
small, positively charged,
dense center of an atom
that contains positively
charged protons, neutral
neutrons, and is
surrounded by empty
space through which one
or more negatively
charged electrons move
• Identify alpha, beta, and
gamma radiations in
terms of composition
and key properties.

4. Section 24.1 Nuclear Radiation (cont.)
radioisotope
X ray
penetrating power
Under certain conditions, some nuclei
can emit alpha, beta, or gamma
radiation.

5. The Discovery of Radiation
• Nuclear reactions are different from other
types of reactions.
• Nuclear chemistry is concerned with the
structure of atomic nuclei and the changes
they undergo.
• Marie Curie and her husband Pierre isolated
the first radioactive materials.

6. The Discovery of Radiation (cont.)

7. Types of Radiation
• Isotopes of atoms with unstable nuclei are
called radioisotopes.
• Unstable nuclei emit radiation to attain more
stable atomic configurations in a process
called radioactive decay.
• The three most common types of radiation
are alpha, beta, and gamma.

8. Types of Radiation (cont.)

9. Types of Radiation (cont.)
• Alpha particles have the same composition
as a helium nucleus—two protons and two
neutrons.
• Because of the protons, alpha particles have
a 2+ charge.
• Alpha radiation consists of a stream of
particles.

10. Types of Radiation (cont.)
• Alpha radiation is not very penetrating—a
single sheet of paper will stop an alpha
particle.

11. Types of Radiation (cont.)
• Beta particles are very fast-moving electrons
emitted when a neutron is converted to a
proton.
• Beta particles have insignificant mass and a
1– charge.

12. Types of Radiation (cont.)
• Beta radiation is a stream of fast moving
particles with greater penetrating power—a
thin sheet of foil will stop them.

13. Types of Radiation (cont.)
• Gamma rays are high-energy
electromagnetic radiation.
• Gamma rays have no mass or charge.
• Gamma rays almost always accompany
alpha and beta radiation.
• X rays are a form of high-energy
electromagnetic radiation emitted from certain
materials in an excited state.

14. Types of Radiation (cont.)
• The ability of radiation to pass through
matter is called its penetrating power.
• Gamma rays are highly penetrating because
they have no charge and no mass.

15. A. A
B. B
C. C
D. D
Section 24.1 Assessment
Why do radioisotopes emit radiation?
A. to balance charges in the nucleus
B. to release energy
C. to attain more stable atomic
configurations
D. to gain energy

16. A. A
B. B
C. C
D. D
Section 24.1 Assessment
X rays are most similar to what type of
nuclear emissions?
A. gamma rays
B. alpha particles
C. beta particles
D. delta waves

18. Section 24.2 Radioactive Decay
• Explain why certain
nuclei are radioactive.
radioactivity: the
process by which some
substances
spontaneously emit
radiation
• Apply your knowledge of
radioactive decay to
write balanced nuclear
equations.
• Solve problems
involving radioactive
decay rates.

19. Section 24.2 Radioactive Decay (cont.)
transmutation
nucleon
strong nuclear force
band of stability
positron emission
Unstable nuclei can break apart
spontaneously, changing the identity of
atoms.
positron
electron capture
radioactive decay series
half-life
radiochemical dating

20. Nuclear Stability
• Except for gamma radiation, radioactive
decay involves transmutation, or the
conversion of an element into another
element.
• Protons and neutrons are referred to as
nucleons.
• All nucleons remain in the dense nucleus
because of the strong nuclear force.

21. Nuclear Stability (cont.)
• The strong nuclear force acts on
subatomic particles that are extremely
close together and overcomes the
electrostatic repulsion among protons.

22. Nuclear Stability (cont.)
• As atomic number increases, more and
more neutrons are needed to produce a
strong nuclear force that is sufficient to
balance the electrostatic repulsion between
protons.
• Neutron to proton ratio increases gradually to
about 1.5:1.

23. Nuclear Stability (cont.)
• The area on the graph
within which all stable
nuclei are found is known
as the band of stability.
• All radioactive nuclei are
found outside the band.
• The band ends at
Pb-208; all elements with
atomic numbers greater
than 82 are radioactive.

24. Types of Radioactive Decay
• Atoms can undergo different types of
decay—beta decay, alpha decay, positron
emission, or electron captures—to gain
stability.

25. Types of Radioactive Decay (cont.)
• In beta decay, radioisotopes above the
band of stability have too many neutrons to
be stable.
• Beta decay decreases the number of
neutrons in the nucleus by converting one to
a proton and emitting a beta particle.

26. Types of Radioactive Decay (cont.)
• In alpha decay, nuclei with more than 82
protons are radioactive and decay
spontaneously.
• Both neutrons and protons must be reduced.
• Emitting alpha particles reduces both
neutrons and protons.

27. Types of Radioactive Decay (cont.)

28. Types of Radioactive Decay (cont.)
• Nuclei with low neutron to proton ratios
have two common decay processes.
• Positron emission is a radioactive decay
process that involves the emission of a
positron from the nucleus.
• A positron is a particle with the same mass
as an electron but opposite charge.

29. Types of Radioactive Decay (cont.)
• During positron emission, a proton in the
nucleus is converted to a neutron and a
positron, and the positron is then emitted.
• Electron capture occurs when the nucleus of
an atom draws in a surrounding electron and
combines with a proton to form a neutron.

30. Types of Radioactive Decay (cont.)

31. Types of Radioactive Decay (cont.)

32. Writing and Balancing Nuclear Equations
• Nuclear reactions are expressed by
balanced nuclear equations.
• In balanced nuclear equations, mass
numbers and charges are conserved.

33. Radioactive Series
• A series of nuclear reactions that begins
with an unstable nucleus and results in the
formation of a stable nucleus is called a
radioactive decay series.

34. Radioactive Decay Rates
• Radioactive decay rates are measured in
half-lives.
• A half-life is the time required for one-half of
a radioisotope to decay into its products.
N is the remaining amount.
N0 is the initial amount.
n is the number of half-lives
that have passed.
t is the elapsed time and T is
the duration of the half-life.

35. Radioactive Decay Rates (cont.)

36. Radioactive Decay Rates (cont.)

37. Radioactive Decay Rates (cont.)
• The process of determining the age of an
object by measuring the amount of certain
isotopes is called radiochemical dating.
• Carbon-dating is used to measure the age of
artifacts that were once part of a living
organism.

38. A. A
B. B
C. C
D. D
A
B
C
D
0% 0%0%0%
Section 24.2 Assessment
The process of converting one element
into another by radioactive decay is
called ____.
A. half-life
B. nuclear conversion
C. transmutation
D. trans-decay

39. A. A
B. B
C. C
D. D
Section 24.2 Assessment
A
B
C
D
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An unknown element has a half-life of 40
years. How much of a 20.0g sample will be
left after 120 years?
A. 0.00g
B. 2.50g
C. 5.00g
D. 7.50g

41. Section 24.3 Nuclear Reactions
• Understand that mass
and energy are related.
mass number: the
number after an
element’s name,
representing the sum of
its protons and neutrons
• Compare and contrast
nuclear fission and
nuclear fusion.
• Explain the process by
which nuclear reactors
generate electricity.

42. Section 24.3 Nuclear Reactions (cont.)
induced transmutation
transuranium element
mass defect
nuclear fission
Fission, the splitting of nuclei, and
fusion, the combining of nuclei, release
tremendous amounts of energy.
critical mass
breeder reactor
nuclear fusion
thermonuclear reaction

43. Induced Transmutation
• One element can be converted into another
by spontaneous emission of radiation.
• Elements can also be forced to transmutate
by bombarding them with high-energy alpha,
beta, or gamma radiation.

44. Induced Transmutation (cont.)
• The process of striking nuclei with high-
velocity charged particles is called induced
transmutation.

45. Induced Transmutation (cont.)
• Particle accelerators used electrostatic and
magnetic fields to accelerate charged
particles to very high speed.
• Transuranium elements are the elements
with atomic numbers 93 and higher,
immediately following uranium.

46. Nuclear Reactions and Energy
• Mass and energy are related.
• Loss or gain in mass accompanies any
reaction that produces or consumes energy.
• ΔE = Δmc2
where E represents energy in
Joules, m mass in kg, and c the speed of
light.

47. Nuclear Reactions and Energy (cont.)
• Most chemical reactions produce or
consume so little energy that the
accompanying changes in mass are
negligible.
• Energy released from nuclear reactions have
significant mass changes.

48. Nuclear Reactions and Energy (cont.)
• The mass of a nucleus is always less than
the sum of the masses of the individual
protons and neutrons that comprise it.
• The difference between a nucleus and its
component nucleons is called the mass
defect.
• Binding together or breaking an atom’s
nucleons involves energy changes.

49. Nuclear Reactions and Energy (cont.)
• Nuclear binding
energy is the
amount of
energy needed
to break 1 mol of
nuclei into
individual
nucleons.

50. Nuclear Fission
• The splitting of nuclei into fragments is
known as nuclear fission.
• Fission is accompanied with a very large
release of energy.

51. Nuclear Fission
• Nuclear power plants use fission to
produce electricity by striking uranium-235
with neutrons.

52. Nuclear Fission (cont.)
• Each fission of U-235 releases two
additional neutrons.
• Each of those neutrons can release two more
neutrons.
• The self-sustaining process is called a chain
reaction.

53. Nuclear Fission (cont.)

54. Nuclear Fission (cont.)
• Without sufficient mass, neutrons escape
from the sample before starting a chain
reaction.
• Samples with enough mass to sustain a chain
reaction are said to have critical mass.

55. Nuclear Fission (cont.)

56. Nuclear Reactors
• Nuclear fission produces the energy
generated by nuclear reactors.
• The fission within a reactor is started by a
neutron-emitting source and is stopped by
positioning the control rods to absorb virtually
all of the neutrons produced in the reaction.

57. Nuclear Reactors (cont.)
• The reactor core contains a reflector that
reflects neutrons back into the core, where
they react with fuel rods.
• Nuclear reactors produce highly radioactive
nuclear waste.
• Breeder reactors produce more fuel than
they consume.

58. Nuclear Reactors (cont.)

59. Nuclear Fusion
• It is possible to bind together two or more
lighter elements (mass number less
than 60).
• The combining of atomic nuclei is called
nuclear fusion.
• Nuclear fusion is capable of releasing very
large amounts of energy.

60. Nuclear Fusion (cont.)
• Fusion has several advantages over
fission.
− Lightweight isotopes are abundant.
− Fusion products are not radioactive.
− However, fusion requires extremely high energies
to initiate and sustain a reaction.

61. Nuclear Fusion (cont.)
• Fusion reactions are also known as
thermonuclear reactions.
• Many problems must be solved before
nuclear fusion is a practical energy source.

62. A. A
B. B
C. C
D. D
A
B
C
D
0% 0%0%0%
Section 24.3 Assessment
Bombarding a nuclei with charged
particle in order to create new elements
is called ____.
A. nuclear conversion
B. nuclear decay
C. induced decay
D. induced transmutation

63. A. A
B. B
C. C
D. D
Section 24.3 Assessment
A
B
C
D
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Thermonuclear reactions involve:
A. splitting nuclei into smaller fragments
B. fusing nuclei together to form
larger particles
C. bombarding nuclei with
charged particles
D. generating electricity in a
nuclear reactor

65. Section 24.4 Applications and Effects of
Nuclear Reactions
• Describe several methods used to detect and
measure radiation.
isotope: an atom of the same element with the same
number of protons but different number of neutrons
• Explain an application of radiation used in the
treatment of disease.
• Describe some of the damaging effects of radiation
on biological systems.

66. Section 24.4 Applications and Effects of
Nuclear Reactions (cont.)
ionizing radiation
radiotracer
Nuclear reactions have many useful
applications, but they also have
harmful biological effects.

67. Detecting Radioactivity
• Radiation with enough energy to ionize
matter it collides with is called ionizing
radiation.
• The Geiger counter uses ionizing radiation to
detect radiation.

68. Detecting Radioactivity (cont.)
• A scintillation counter detects bright flashes
when ionizing radiation excites electrons of
certain types of atoms.

69. Uses of Radiation
• When used safely, radiation can be very
useful.
• A radiotracer is a radioactive isotope that
emits non-ionizing radiation and is used to
signal the presence of an element or specific
substrate.

70. Uses of Radiation (cont.)
• Radiation can damage or destroy healthy
cells.
• Radiation can also destroy unhealthy cells,
such as cancer cells.
• Unfortunately, radiation therapy also destroys
healthy cells in the process of destroying
cancerous cells.

71. Biological Effects of Radiation
• Radiation can be very harmful.
• The damage depends on type of radiation,
type of tissue, penetrating power, and
distance from the source.

72. Biological Effects of Radiation (cont.)
• High energy radiation is dangerous
because it produces free radicals.
• Free radicals are atoms or molecules that
contain one or more unpaired electrons.
• Free radicals are highly reactive.

73. Biological Effects of Radiation (cont.)
• Two units measure doses of radiation.
• The rad stands for Radiation-Absorbed Dose,
which is the amount of radiation that results in
0.01 J of energy per kilogram of tissue.
• The rad does not account for the type of
tissue that is absorbing the radiation.
• The rad is multiplied by a factor related to its
effect on the tissue involved and is called the
rem, Roentgen Equivalent for Man.

74. Biological Effects of Radiation (cont.)

75. Biological Effects of Radiation (cont.)
• I1
d1
2
= I2
d2
2
where I = intensity and
d = distance.

76. A. A
B. B
C. C
D. D
A
B
C
D
0% 0%0%0%
Section 24.4 Assessment
What is a radioisotope that emits non-
ionizing radiation and is used to signal the
presence of certain elements called?
A. rad
B. rem
C. radiotracer
D. free radical

77. A. A
B. B
C. C
D. D
Section 24.4 Assessment
A
B
C
D
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Radiation with enough energy to cause
tissue damage by ionizing the particles it
collides with is called ____.
A. alpha decay
B. beta decay
C. gamma radiation
D. ionizing radiation

79. Chemistry Online
Study Guide
Chapter Assessment
Standardized Test Practice
Image Bank
Concepts in Motion

80. Section 24.1 Nuclear Radiation
Key Concepts
• Wilhelm Roentgen discovered X rays in 1895.
• Henri Becquerel, Marie Curie, and Pierre Curie
pioneered the fields of radioactivity and nuclear
chemistry.
• Radioisotopes emit radiation to attain more-stable
atomic configurations.

81. Section 24.2 Radioactive Decay
Key Concepts
• The conversion of an atom of one element to an atom of
another by radioactive decay processes is called
transmutation.
• Atomic number and mass number are conserved in
nuclear reactions.
• A half-life is the time required for half of the atoms in a
radioactive sample to decay.
• Radiochemical dating is a technique for determining the
age of an object by measuring the amount of certain
radioisotopes remaining in the object.

82. Section 24.3 Nuclear Reactions
Key Concepts
• Induced transmutation is the bombardment of nuclei
with particles in order to create new elements.
• In a chain reaction, one reaction induces others to
occur. A sufficient mass of fissionable material is
necessary to initiate the chain reaction.
• Fission and fusion reactions release large amounts of
energy.
E = mc2

83. Section 24.4 Applications and Effects
of Nuclear Reactions
Key Concepts
• Different types of counters are used to detect and
measure radiation.
• Radiotracers are used to diagnose disease and to
analyze chemical reactions.
• Short-term and long-term radiation exposure can cause
damage to living cells.

84. A. A
B. B
C. C
D. D
The half-life of a radioisotope is:
A. one-half its total life
B. 2500 years
C. the amount of time it takes
to completely decay
D. the amount of time it takes
for one-half to decay

85. A. A
B. B
C. C
D. D
A
B
C
D
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What is a positron?
A. a nucleon with the same mass as
a neutron and a positive charge
B. a nucleon with the same mass as
a proton and a negative charge
C. a nucleon with the same mass as
an electron and a positive charge
D. a type of radioactive emission with
a negative charge

86. A. A
B. B
C. C
D. D
A
B
C
D
0% 0%0%0%
What is the force that holds the protons
and neutrons together in the nucleus of an
atom?
A. nuclear magnetic force
B. strong nuclear force
C. ionic bonding
D. nuclear bond

87. A. A
B. B
C. C
D. D
A
B
C
D
0% 0%0%0%
During positron emission, a proton is
converted to:
A. a neutron and electron
B. an electron and positron
C. a proton and neutron
D. a neutron and positron

88. A. A
B. B
C. C
D. D
A
B
C
D
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A thermonuclear reaction is also
called ____.
A. nuclear fission
B. nuclear fusion
C. mass defect
D. critical mass

89. A. A
B. B
C. C
D. D
A
B
C
D
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Which statement is NOT true of beta
particles?
A. They have the same mass as an electron.
B. They have a charge of 1+.
C. They are less penetrating
than alpha particles.
D. They are represented by 0
-1
β.

90. A. A
B. B
C. C
D. D
A
B
C
D
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The site that oxidation occurs at in a
battery is called ____.
A. anode
B. cathode
C. nothode
D. salt bridge

91. A. A
B. B
C. C
D. D
A
B
C
D
0% 0%0%0%
A solution of 0.500M HCl is used to titrate
15.00mL if KOH solution. The end point of
the titration is reached after 25.00 mL of
HCl is added. What is the concentration
of KOH?
A. 9.00M
B. 1.09M
C. 0.833M
D. 0.015M

92. A. A
B. B
C. C
D. D
A
B
C
D
0% 0%0%0%
The half-life of K-40 is 1.26 × 109
years.
How much of a 10.0g sample will be left
after 200 million years?
A. 8.96g
B. 8.03g
C. 7.75g
D. 4.99g

93. A. A
B. B
C. C
D. D
A
B
C
D
0% 0%0%0%
Elements above the band of stability are
radioactive and decay by ____.
A. alpha decay
B. beta decay
C. positron emission
D. electron capture

94. Click on an image to enlarge.

118. 3 Radioactive Decay Processes
.16 Chain Reactions
.17 Critical Mass
.20 Nuclear Power Plants

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