Nuclear Changes

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Nuclear Changes

• Honors Class Start Here.
• Chemistry 1 jump to slide 38

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Radioactivity

• process by which an unstable nucleus emits one or
  more particles or energy in the form of
  electromagnetic radiation.

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Examine these isotopes. Which would be the must
abundant? Why?
Think-Timed Pair Share
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Nuclear decay

• Radioactive materials have unstable nuclei.
• These nuclei go through changes by emitting
  particles or releasing energy.
• After the changes in the nucleus, the element can

• transform into a different isotope of the same
  element or

• change into an entirely different element.

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Nuclear radiation

• charged particles or energy emitted by an
  unstable nucleus
• Nuclear radiation is associated with nuclear
  changes

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Four types of nuclear radiation

• Alpha Particles
• Beta Particles
• Gamma Rays
• Neutron Emission

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Alpha particle (a)

• An alpha particle is a positively charged
  particle, emitted by some radioactive nuclei that
  consists of two protons and two neutrons
• Alpha particles have a 2 charge.
• Although an alpha particle has a 2 charge as one
  would predict from the two protons, it is heavier
  with a mass of 4 amu.
• Where does the extra mass come from?

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• The alpha particle is also depicted as

Mass Number
42He
Atomic Number
9

• The alpha particle is depicted as

Mass Number
or
42He
a
Atomic Number
Protons
Neutrons
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• The emission of an alpha particle from the
  nucleus of an atom decreases
• the nuclear charge number by two
• the mass number by four.

a
23090 Th ? 22688Ra 42He
156 C ? 42He 114Be
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a
156C
156 C ? 42He 114Be
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114Be
156C
42He
a
156 C ? 42He 114Be
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• The emission of an alpha particle from the
  nucleus of an atom decreases the nuclear charge
  (atomic number) by two.

23090 Th ? 22688Ra 42He
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Beta particle (ß)

• an electron emitted during the radioactive decay
  of a neutron in an unstable nucleus
• Like an electron, it has no mass and a 1 charge.
• It is depicted as

0-1e
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• A beta particle is created in the nucleus by a
  process in which one neutron is transformed into
  

a proton
a beta particle
Neutron
Proton

Electron
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Total mass and charge is conserved. Mass
63 63 0 63 63 Charge 28
29 (-1) 28 28
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Radioactive Decay
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Gamma ray

• high-energy electromagnetic radiation emitted by
  a nucleus during radioactive decay.

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Gamma Rays

• Electromagnetic radiation with the
• Highest energy and
• shortest wavelength,
• Used to kill certain brain tumors
• Used in sterilization and disinfection of

Food
Medical Supplies
Hygienic Products
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Types of Radiation
Sheet of paper
Block of wood
Concrete wall
Alpha
Beta
Gamma
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Neutron Emission (10n)

• the release of a high-energy neutron by some
  neutron-rich nuclei during radioactive decay.

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Nuclear Decay

• A nucleus gives up two protons and two neutrons
  during alpha decay
• A nucleus gains a proton and loses a neutron
  during beta decay.

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Radioactive Decay Rates

• Half-life the time required for half a sample
  of radioactive nuclei to decay

After the next half-life, half the remaining
substance decays leaving only a quarter of the
sample undecayed.

• Half-life is a measure of how quickly a
  substance decays.

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Mass of Half-Lives Time
10.0 g 0 0
5.0 g 1 5.27
2.5 g 2 10.54
15.81
Time of Decay of Half-lives
Time per Half-Life
Fill in the last two boxes of the table.
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Nuclear Forces

• Strong nuclear force the interaction that binds
  protons and neutrons together in a nucleus over a
  short distance.
• This nuclear force is strong enough to overcome
  the strong electrostatic repulsion between the
  protons.

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Nuclear Fission

• the process by which a nucleus splits into two or
  more smaller fragments releasing neutrons and
  energy.

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Special Theory of Relativity

• Presented by Albert Einstein
• means that matter can be converted into energy
  and energy into matter.
• Energy mass X (speed of light)2
• Emc2

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Neutrons released by fission can start a chain
reaction

• Nuclear chain reaction a series of fission
  processes in which the neutrons emitted by a
  dividing nucleus cause the division of other
  nuclei.

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• 23592U 10n ? 13856Ba 9536Kr 3 10n

92 0 56
36 0
The total of the atomic numbers (number of
protons) on the reactant side is equal to the
total of the atomic numbers (number of protons)
on the product side.
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• 23592U 10n ? 13856Ba 9536Kr 3 10n

235 1 138
95 3 (1)

• The total of the mass numbers on the reactant
  side is equal to the total of the mass numbers on
  the product side.

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• Chain reactions can be controlled
• These characteristics behind nuclear fission are
  what brought about the nuclear age and the
  atomic/nuclear bombs.

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Contrast Fission with Nuclear Fusion

• Nuclear fusion is the process in which light
  nuclei combine at extremely high temperatures,
  forming heavier nuclei and releasing energy.
• The fusion of four hydrogen atoms into one helium
  atom is what stars (which include our sun) do.
• This lets off enormous amounts of energy in the
  form of gamma rays.

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Nuclear Power

• Nuclear Fission
• Nuclear Fusion

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Nuclear Fission

• the process by which a nucleus splits into two or
  more smaller fragments releasing neutrons and
  energy.

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Fission

• The breaking apart of a large nucleus into two
  smaller nuclei
• 10 n 23592 U ? 14156 Ba 9236 Kr 3 10 n
• Occurs in nuclear power plants

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Nuclear Fission
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Fission Chain Reaction
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Nuclear Reactor
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Nuclear fission

• The break down of a single nucleus of an atom
  produces a tremendous amount of energy.
• No gaseous pollutants are produced.
• Very little radioactive material is needed.
• Safe operation of a nuclear power plant and
  disposal of radioactive wastes are essential.

45
Nuclear Waste

• Waste from Fission Reactors contain isotopes with
  half-lives of thousands to hundreds of thousands
  of years. Storage containers only last decades.
• Other waste comes from uranium mills, research
  labs, medical diagnostic and treatment facilities
  and former nuclear weapon production facilities.

Where and how should the waste be stored until it
is safe?
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Nuclear Fusion

• For a fusion reaction to occur it is necessary to
  bring the nuclei so close together that nuclear
  forces become important and "glue" the nuclei
  together. The nuclear force only acts over
  incredibly small distances and has to counteract
  the electrostatic force where the positively
  charged nuclei repel each other. For these
  reasons fusion most easily occurs in a high
  density, high temperature environment.
• On Earth, nuclear fusion was first reached in the
  explosion of the Hydrogen bomb. In a
  non-desctructive manner, fusion has also been
  reached in different experimental devices aimed
  at studying the possibility of producing energy
  in a controlled fashion.

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Nuclear Fusion

• The process in which light nuclei combine at
  extremely high temperatures, forming heavier
  nuclei and releasing energy.
• The fusion of four hydrogen atoms into one helium
  atom is what stars (which include our sun) do.
• This lets off enormous amounts of energy in the
  form of gamma rays.

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Nuclear Fusion

• The joining of smaller nuclei to make a larger
  nucleus produces a tremendous amount of energy.
• Nuclear fusion is what is used in older stars and
  our sun to produce heat, light and other
  radiation.
• Fusion can produce fast neutrons, a highly
  energetic and potentially dangerous form of
  nuclear radiation.
• Production of energy using nuclear fusion is
  extremely costly because a tremendous amount of
  energy is needed to bring 2 nuclei close enough
  to fuse. It would take a fission bomb to produce
  enough energy to start a fusion reaction!

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Energy Source of Future
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Nuclear Fusion
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Applications of Decay Reactions

• Radioisotopes are used to analyze matter, study
  plant growth, diagnose medical problems, and
  treat diseases.

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Open Note ReviewUse Rally Coach to Review

• What are the 2 symbols for the
• a. Alpha particles?
• b. Beta particles?
• c. Gamma rays?
• How is the mass number determined?
• How is the atomic number determined?
• Label the mass number atomic number for each
  particle of radiation.
• How is the structure of atoms altered during
  fission?
• How is the structure of atoms altered during
  fusion?
• What nuclear process occurs in the sun?
• What nuclear process do we currently use to
  produce power?
• Remember, one paper per group of two. Remember
  Praise!

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• Additional HONORS Rally Coach Practice.
• Fill in the blanks.
• These are __________ decay reactions.
• 22286Rn ? _______ 42He
• 20985At ? _______ 42He
• 23792U ? _______ 42He
• These are __________ decay reactions.
• 14056Ba ? _______ 0-1e
• 6027Co ? _______ 0-1e
• 146C ? _______ 0-1e
• 21083Bi ? _______ 0-1e

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• Fill in the blanks.
• Balance and determine if these are a or ß decay
  reactions.
• 21082Pb ? 21083Bi _______
• 23191Pa ? 22789Ac _______
• 14962Sm ? 14560Nd _______
• 22789Ac ? 22790Th _______

0-1e
42He
42He
0-1e
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Honors Quiz

• Quiz A
• Write the nuclear equation for the alpha decay of
  astatine-213.
• Write the nuclear equation for the beta decay of
  titanium-50.
• Quiz B
• Write the nuclear equation for the alpha decay of
  bismuth-209.
• Write the nuclear equation for the beta decay of
  actinium-226.

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Half-Life of Skittles

• Modeling Radioactive Decay

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• Procedures
• Label the ziplock bags 1 RADIOACTIVE and 2
  STABLE
• Wash and dry hands.
• Exam all skittles to make sure that they all have
  the letter s written on them.
• Remove (and eat) any skittle that has no markings
  on it.
• Record how long it takes you to count the
  remaining skittles.
• Record the time it takes to count the skittles
  that you are starting with, and also record how
  many skittles that you have to start with now.
  This is the number of skittles on your data table
  for toss 0.
• Place all these skittles into ziplock bag 1.

S
stable
radioactive isotope
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• Lay construction paper down in the lab tray so
  that the skittles dont touch the lab tray
  (chemicals could still be there).
• Mix the skittles in the ziplock bag 1. Be
  gentle with the skittles because you dont want
  to lose any of them.Carefully take the bag of
  skittles and spill them onto the construction
  paper.
• Separate the skittles that have the s facing up
  from the skittles that have the s facing down.
  Count the number of skittles with the s facing
  up. These skittles have undergone radioactive
  decay and are now stable. Record this amount
  next to the toss number. So if this is your
  first toss, this toss number would be 1. Remove
  only the skittles with the s facing up and
  place them into ziplock bag 2.
• Calculate the number of skittles remaining, or
  count the number remaining.For example, suppose
  you started with 250 pieces, after your first
  toss you removed 40 pieces. The number of tosses
  would be 1, the number of pieces removed would be
  40, and the number of pieces remaining would be
  the total number you started with minus the
  number of pieces removed (250-40210). Record
  the amount of radioactive isotope remaining in
  your chart, and return them to Bag 1
• Repeat steps 9-11 until four or fewer pieces of
  candy remain.

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Tosses Skittles Removed Skittles Remaining
0 0
1
2
3
4
5
6
7
8
9
10
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Modeling Nuclear Decay Graph

• Make a full page graph of tosses versus pieces of
  candy remaining.
• Place the number of tosses on the x-axis and the
  number of pieces of candy remaining on the
  y-axes.
• Start your graph at zero tosses with all of the
  pieces of candy you started with.
• Determine the half-life of the decaying skittles
  in the following manner.
• Find the point on the graph that corresponds to
  one-half of the original number of skittles.
• Move vertically down from this point until you
  reach the horizontal axis.
• Your answer will be the number of tosses
  multiplied by the original amount of time it took
  you to count the skittles.

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Analysis and Conclusion

• Questions Answer on a separate sheet of paper.
• What is the shape of your graph?
• How many tosses are required to remove one-half
  of the skittles?
• How many tosses are required to remove one-fourth
  of the skittles?
• Conclusion
• Assume each toss is equal to one year instead of
  the seconds you recorded, what is the half-life
  of the skittles in years?
• Using your answer from questions 4, how many
  skittles should remain after
• 8 years?
• 12 years?
• Do these numbers agree with your observation?
• What factor(s) could account for differences in
  your observed results and those you calculated?
• Would the determined half-life be different if
  you used a larger number of skittles?