Chemistry: Matter and Change

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Chapter Menu
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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Section 24-1
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.

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Section 24-1
Section 24.1 Nuclear Radiation (cont.)
radioisotope X ray penetrating power
Under certain conditions, some nuclei can emit
alpha, beta, or gamma radiation.
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Section 24-1
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.

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Section 24-1
The Discovery of Radiation (cont.)
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Section 24-1
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.

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Section 24-1
Types of Radiation (cont.)
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Section 24-1
Types of Radiation (cont.)

• Alpha particles have the same composition as a
  helium nucleustwo protons and two neutrons.

• Because of the protons, alpha particles have a 2
  charge.
• Alpha radiation consists of a stream of particles.

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Section 24-1
Types of Radiation (cont.)

• Alpha radiation is not very penetratinga single
  sheet of paper will stop an alpha particle.

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Section 24-1
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.

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Section 24-1
Types of Radiation (cont.)

• Beta radiation is a stream of fast moving
  particles with greater penetrating powera thin
  sheet of foil will stop them.

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Section 24-1
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.

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Section 24-1
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.

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Section 24-1
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

1. A
2. B
3. C
4. D

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Section 24-1
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

1. A
2. B
3. C
4. D

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End of Section 24-1
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Section 24-2
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.

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Section 24-2
Section 24.2 Radioactive Decay (cont.)
transmutation nucleon strong nuclear force band
of stability positron emission
positron electron capture radioactive decay
series half-life radiochemical dating
Unstable nuclei can break apart spontaneously,
changing the identity of atoms.
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Section 24-2
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.

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Section 24-2
Nuclear Stability (cont.)

• The strong nuclear force acts on subatomic
  particles that are extremely close together and
  overcomes the electrostatic repulsion among
  protons.

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Section 24-2
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 1.51.

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Section 24-2
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.

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Section 24-2
Types of Radioactive Decay

• Atoms can undergo different types of decaybeta
  decay, alpha decay, positron emission, or
  electron capturesto gain stability.

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Section 24-2
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.

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Section 24-2
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.

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Section 24-2
Types of Radioactive Decay (cont.)
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Section 24-2
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.

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Section 24-2
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.

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Section 24-2
Types of Radioactive Decay (cont.)
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Section 24-2
Types of Radioactive Decay (cont.)
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Section 24-2
Writing and Balancing Nuclear Equations

• Nuclear reactions are expressed by balanced
  nuclear equations.

• In balanced nuclear equations, mass numbers and
  charges are conserved.

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Section 24-2
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.

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Section 24-2
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.
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Section 24-2
Radioactive Decay Rates (cont.)
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Section 24-2
Radioactive Decay Rates (cont.)
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Section 24-2
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.

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Section 24-2
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

1. A
2. B
3. C
4. D

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Section 24-2
Section 24.2 Assessment
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

1. A
2. B
3. C
4. D

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End of Section 24-2
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Section 24-3
Section 24.3 Nuclear Reactions

• Understand that mass and energy are related.

mass number the number after an elements 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.

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Section 24-3
Section 24.3 Nuclear Reactions (cont.)
induced transmutation transuranium element mass
defect nuclear fission
critical mass breeder reactor nuclear
fusion thermonuclear reaction
Fission, the splitting of nuclei, and fusion, the
combining of nuclei, release tremendous amounts
of energy.
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Section 24-3
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.

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Section 24-3
Induced Transmutation (cont.)

• The process of striking nuclei with high-velocity
  charged particles is called induced transmutation.

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Section 24-3
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.

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Section 24-3
Nuclear Reactions and Energy

• Mass and energy are related.

• Loss or gain in mass accompanies any reaction
  that produces or consumes energy.
• ?E ?mc2 where E represents energy in Joules, m
  mass in kg, and c the speed of light.

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Section 24-3
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.

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Section 24-3
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 atoms nucleons
  involves energy changes.

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Section 24-3
Nuclear Reactions and Energy (cont.)

• Nuclear binding energy is the amount of energy
  needed to break 1 mol of nuclei into individual
  nucleons.

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Section 24-3
Nuclear Fission

• The splitting of nuclei into fragments is known
  as nuclear fission.

• Fission is accompanied with a very large release
  of energy.

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Section 24-3
Nuclear Fission

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

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Section 24-3
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.

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Section 24-3
Nuclear Fission (cont.)
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Section 24-3
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.

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Section 24-3
Nuclear Fission (cont.)
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Section 24-3
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.

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Section 24-3
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.

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Section 24-3
Nuclear Reactors (cont.)
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Section 24-3
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.

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Section 24-3
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.

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Section 24-3
Nuclear Fusion (cont.)

• Fusion reactions are also known as thermonuclear
  reactions.

• Many problems must be solved before nuclear
  fusion is a practical energy source.

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Section 24-3
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

1. A
2. B
3. C
4. D

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Section 24-3
Section 24.3 Assessment
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

1. A
2. B
3. C
4. D

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End of Section 24-3
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Section 24-4
Section 24.4 Applications and Effects of Nuclear
Reactions

• Describe several methods used to detect and
  measure radiation.

• Explain an application of radiation used in the
  treatment of disease.
• Describe some of the damaging effects of
  radiation on biological systems.

isotope an atom of the same element with the
same number of protons but different number of
neutrons
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Section 24-4
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.
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Section 24-4
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.

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Section 24-4
Detecting Radioactivity (cont.)

• A scintillation counter detects bright flashes
  when ionizing radiation excites electrons of
  certain types of atoms.

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Section 24-4
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.

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Section 24-4
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.

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Section 24-4
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.

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Section 24-4
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.

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Section 24-4
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.

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Section 24-4
Biological Effects of Radiation (cont.)
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Section 24-4
Biological Effects of Radiation (cont.)

• I1d12 I2d22 where I intensity and d
  distance.

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Section 24-4
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

1. A
2. B
3. C
4. D

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Section 24-4
Section 24.4 Assessment
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

1. A
2. B
3. C
4. D

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End of Section 24-4
79
Resources Menu
Chemistry Online Study Guide Chapter
Assessment Standardized Test Practice Image
Bank Concepts in Motion
80
Study Guide 1
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.

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Study Guide 2
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.

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Study Guide 3
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

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Study Guide 4
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.

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Chapter Assessment 1
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

1. A
2. B
3. C
4. D

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Chapter Assessment 2
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

1. A
2. B
3. C
4. D

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Chapter Assessment 3
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

1. A
2. B
3. C
4. D

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Chapter Assessment 4
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

1. A
2. B
3. C
4. D

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Chapter Assessment 5
A thermonuclear reaction is also called ____.
A. nuclear fission B. nuclear fusion C. mass
defect D. critical mass

1. A
2. B
3. C
4. D

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STP 1
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 0-1ß.

1. A
2. B
3. C
4. D

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STP 2
The site that oxidation occurs at in a battery is
called ____. A. anode B. cathode C. nothode
D. salt bridge

1. A
2. B
3. C
4. D

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STP 3
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

1. A
2. B
3. C
4. D

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STP 4
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

1. A
2. B
3. C
4. D

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STP 5
Elements above the band of stability are
radioactive and decay by ____. A. alpha decay
B. beta decay C. positron emission D. electron
capture

1. A
2. B
3. C
4. D

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CIM
Table 24.3 Radioactive Decay Processes Figure
24.16 Chain Reactions Figure 24.17 Critical
Mass Figure 24.20 Nuclear Power Plants
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