Intro to Nuclear Chemistry

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Intro to Nuclear Chemistry
http//www.chem.orst.edu/graduate/pics/Reactor.jpg
PowerPoint basics from Mrs. Coyle and other
Internet Sources
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Learning Objectives

• TLW understand the basic process of nuclear
  chemistry (TEKS 12)
• TLW be able to describe alpha, beta, and gamma
  radiation (TEKS 12.A)
• TLW describe radioactive decay process in terms
  of balanced nuclear equations (TEKS 12.B)
• TLW compare fission and fusion reactions (TEKS
  12.C)

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Anticipatory Exercise

• Background Radiation Whats YOUR Exposure?
• Flinn Scientific ChemTopicTM Labs Book 18, page
  2

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How does a nuclear reactor work?
http//www.lanl.gov/science/1663/images/reactor.jp
g
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How does a small mass contained in this bomb
cause

• Nuclear Bomb of 1945 known as fat man

http//www.travisairmuseum.org/assets/images/fatma
n.jpg
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this huge nuclear explosion?
http//library.thinkquest.org/06aug/01200/Graphics
/705px-Nuclear_fireball.jpg
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Is there radon in your basement?
http//a.abcnews.com/images/Blotter/abc_1radon_ad_
070625_ssh.jpg
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Nuclear Notation

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Practice Using Nuclear Notation

• How would you write the following elements using
  nuclear notation?
• H
• C
• Co
• U

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Nucleons

• Protons and Neutrons
• The nucleons are bound together by the strong
  force.

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Isotopes

• Atoms of a given element with
• same protons
• but
• different neutrons

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• H H H

http//education.jlab.org/glossary/isotope.html
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Isotopes of Carbon
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Radioactive Isotopes

• Isotopes of certain unstable elements that
  spontaneously emit particles and energy from the
  nucleus.
• Henri Beckerel 1896 accidentally observed
  radioactivity of uranium salts that were fogging
  photographic film.
• His associates were Marie and Pierre Curie.

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Marie Curie 1867 - 1934, in Poland as Maria
Sklodowska

• Lived in France
• 1898 discovered the elements polonium and radium.

http//www.radiochemistry.org/nuclearmedicine/pion
eers/images/mariecurie.jpg
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Marie Curie a Pioneer of Radioactivity

• Winner of 1903 Nobel Prize for Physics with Henri
  Becquerel and her husband, Pierre Curie (1859
  1906)
• Winner of the sole 1911 Nobel Prize for Chemistry
• Sadly, she and Pierre died of radiation poisoning

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General Nuclear Equations

• Handout of Graphic Organizer on General Nuclear
  Equations

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3 Main Types of Radioactive Decay

• Alpha a
• Beta b
• Gamma g

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Alpha Decay

• Emission of alpha particles a
• helium nuclei
• two protons and two neutrons
• charge 2e 
• can travel a few inches through air
• can be stopped by a sheet of paper, clothing.

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Alpha Decay
Uranium Thorium
alpha particle
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Alpha Decay
http//education.jlab.org/glossary/alphadecay.gif
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Beta Decay

• Beta particles b electrons ejected from the
  nucleus when neutrons decay
• ( no ? p b- )
• Beta particles have the same charge and mass as
  "normal" electrons.

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Beta Decay

• Beta particles b electrons ejected from the
  nucleus when neutrons decay
• no ? p b-
• Beta particles have the same charge and mass as
  "normal" electrons.
• Can be stopped by aluminum foil or a block of
  wood.

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Beta Decay
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Beta Decay
Thorium
Protactinium beta particle
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Gamma Decay

• Gamma radiation g electromagnetic energy that
  is released. 
• Gamma rays are electromagnetic waves.
• They have no mass.
• Gamma radiation has no charge.
• Most Penetrating, can be stopped by 1 m thick
  concrete or a several cm thick sheet of lead.

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Examples of Radioactive Decay

• Alpha Decay
• Po ? Pb He
• Beta Decay p? n e
• n ? p e
• C ? N e
• Gamma Decay
• Ni ? Ni g
• (excited nucleus)

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Which is more penetrating potentially more
harmful? Why?
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Second Graphic Organizer

• Nuclear Decay Organizer (pdf) - link

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Part II

• Balancing Nuclear Equations

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Balancing Nuclear Reactions

• In the reactants (starting materials on the
  left side of an equation) and products (final
  products on the right side of an equation)
  Law of Conservation of Mass
• Atomic numbers must balance
• and
• Mass numbers must balance
• Use a particle or isotope to fill in the missing
  protons and neutrons

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Nuclear Reactions

• Alpha emission

Note that mass number (A) goes down by 4 and
atomic number (Z) goes down by 2.
Nucleons (nuclear particles protons and
neutrons) are rearranged but conserved
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Nuclear Reactions

• Beta emission

Note that mass number (A) is unchanged and atomic
number (Z) goes up by 1.
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Other Types of Nuclear Reactions

• Positron (01b) a positive electron

Electron capture the capture of an electron
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Learning Check

• What radioactive isotope is produced in the
  following bombardment of boron?
• 10B 4He ? 1n
• 5 2
  0

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Write Nuclear Equations!

• Write the nuclear equation for the beta emitter
  Co-60.

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Group Practice

• Work some problems together using ELMO
• See Nuclear Equations Worksheet page 4 of Flinn
  ChemTopicTM Labs book (vol. 18)

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Independent Practice Set

• Balancing Nuclear Equations 1
• Balancing Nuclear Equations 2 (Word Problems)

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Part III

• Nuclear Stability
• Half-Life

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Introduce Half-Life with Lab

• Half-Life of MMs (TAMU handout) or
• Half-Life of Licorice (TAMU Handout) or
• Half-Life with Pennies
• IPC Lab Manual pages 152 153

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Nuclear Stability

• Depends on the neutron to proton ratio.

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Band of Stability
Number of Neutrons, (N)
Number of Protons (Z)
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What happens to an unstable nucleus?

• They will undergo decay
• The type of decay depends on the reason for the
  instability

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What type of decay will happen if the nucleus
contains too many neutrons?

• Beta Decay

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Example
14
0
14

• C ? N e
• In N-14 the ratio of neutrons to protons is 11

-1
6
7
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• Nuclei with atomic number gt 83 (Bismuth) are
  radioactive

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Radioactive Half-Life (t1/2 )

• Through study of radioactive isotopes, scientists
  have defined the rate of instability as half-life
• In other words. The time for half of the
  radioactive nuclei in a given sample to undergo
  decay

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Common Radioactive Isotopes
Isotope Half-Life Radiation
Emitted Carbon-14 5,730 years b,
g Radon-222 3.8 days a Uranium-235 7.0 x
108 years a, g Uranium-238 4.46 x 109 years
a
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Radioactive Half-Life

• After one half life there is 1/2 of original
  sample left.
• After two half-lives, there will be
• 1/2 of the 1/2 1/4 the original sample.
• After three half-lives, there will be 1/2 of the
  1/4 (or 1/8) the original sample
• .And so on.

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Graph of Amount of Remaining Nuclei vs Time
AAoe-lt
A
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Half-Life Related Calculations

• How to calculate number of half-lives (1/2 x
  1/2x)
• How to calculate how old something is (no. of
  half-lives x time per half-life)
• Calculate amount remaining (A) after a certain
  number of half-lives
• A Ao (where Ao original amount)
• 2n (where n no. of half-lives)
• Calculate percentage remaining
• __1_x 100
• 2n (where n no. of half-lives)

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Example

• You have 100 g of radioactive C-14. The half-life
  of C-14 is 5,730 years.
• How many grams are left after one half-life?
  Answer 100 g
• 50 g
• How many grams are left after two half-lives?

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Problem

• A sample of 3x107 Radon atoms are trapped
• in a basement that is sealed. The half-life of
• Radon is 3.83 days. How many radon atoms
• are left after 31 days?
• answer1.2x105 atoms

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Group and Independent Practice

• Determining Half-Lives Practice Set
• Practice 2 of problems as a group

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• Part IV
• Fission and Fusion

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From Bill Nye the Science Guy

• Nuclear Power link to Discovery Education
  website

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• FISSION

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Nuclear Fission
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Nuclear Fission

• Fission is the splitting of atoms
• These are usually very large, so that they are
  not as stable
• Fission chain has three general steps
• 1. Initiation. Reaction of a single atom
  starts the chain (e.g., 235U neutron)
• 2. Propagation. 236U fission releases neutrons
  that initiate other fissions
• 3. Produces enormous amounts of energy

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Nuclear Fission POWER

• Currently about 103 nuclear power plants in the
  U.S. and about 435 worldwide.
• 17 of the worlds energy comes from nuclear.

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Figure 19.6 Diagram of a nuclear power plant.
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Fission

• Benefits
• A lot of energy can be produced from a small
  amount of raw material
• 1 ton of nuclear material 1 million tons of
  coal or 1 million barrels of oil
• Clean source of energy generation not air
  polluting like fossil fuels
• Long term source of fuel

• Concerns
• Safety accidents have potential for horrendous
  harm (immediate and long term, such as cancer)
• No good way to dispose of high level nuclear
  waste
• Expensive construction and maintenance costs

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• FUSION

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Nuclear Fusion

• Fusion
• small nuclei combine
• 2H 3H 4He 1n
• 1 1
  2 0
• Occurs in the sun and other stars

Energy
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Nuclear Fusion

• Fusion
• Excessive heat can not be contained
• Attempts at cold fusion have FAILED.
• Hot fusion is difficult to contain

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Fusion

• Benefits
• A lot of energy can be produced from a small
  amount of raw material
• 1 ton of nuclear material 1 million tons of
  coal or 1 million barrels of oil
• Clean source of energy generation not air
  polluting like fossil fuels
• Long term source of fuel
• Doesnt create hazardous radioactive wastes as
  does nuclear fission

• Concerns
• Occur at extremely high temperatures like that
  of sun
• Cannot sustain the reactions long enough to be
  useful for power generation
• Safety accidents have potential for horrendous
  harm (immediate and long term, such as cancer)
• Expensive construction and maintenance costs

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• Part V
• Uses of Nuclear Chemistry

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Radiocarbon Dating

• Radioactive C-14 is formed in the upper
  atmosphere by nuclear reactions initiated by
  neutrons in cosmic radiation
• 14N 1on ---gt 14C 1H
• The C-14 is oxidized to CO2, which circulates
  through the biosphere.
• When a plant dies, the C-14 is not replenished.
• But the C-14 continues to decay with t1/2 5,730
  years.
• Activity of a sample can be used to date the
  sample.

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Nuclear Medicine Imaging
Thyroid imaging using Tc-99m
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Food Irradiation

• Food can be irradiated with g rays from 60Co or
  137Cs.
• Irradiated milk has a shelf life of 3 mo. without
  refrigeration.
• USDA has approved irradiation of meats and eggs.

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• Part VI
• Hazards of Radiation

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Effects of Radiation
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Summary

• Nuclear Radiation can be naturally occurring or
  man-made
• Most of radiation we are exposed to is naturally
  occurring alpha rays
• Alpha Radiation weakest (blocked by paper or
  cloth)
• Beta Radiation medium (blocked by wood or foil)
• Gamma Radiation strongest (blocked by lead or
  concrete)
• Key Nuclear Science Pioneers Henri Beckerel,
  Marie and Pierre Curie

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Summary

• How to Write Nuclear Notation - see blue graphic
  organizer
• Symbols for
• Beta Particles Alpha Particles
• Positrons Neutrons
• Gamma Rays ?

Atomic Mass
Element symbol
Atomic No.
1n 0
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Summary

• Balancing Nuclear Equations (Law of Conservation
  of Mass)
• Add coefficients in front of nuclear particles

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SUMMARY - Half-Life Calculations

• How to calculate number of half-lives (1/2 x ½
  x) or
• 1/amount remaining (as decimal or fraction) 2n
  where n no. half-lives
• remember percent remaining 100 percent
  decayed
• How to calculate how old something is (no. of
  half-lives x time per half-life)
• Calculate amount remaining (A) after a certain
  number of half-lives
• A Ao (where Ao original amount)
• 2n (where n no. of half-lives)
• Calculate percentage remaining
• __1_x 100
• 2n (where n no. of half-lives)

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Summary

• Describe the difference between
• fission (splitting atoms)
• 3 steps
• Initiation
• Propagation
• Production of large amounts of energy
• fusion (combining nuclei)
• Describe the pros and cons of each
• Describe examples of fission and fusion
• Examples of beneficial and harmful radiation
  sources
• Power generation
• Medical imaging, diagnostics, disease treatments
• Food safety
• Other historical dating, smoke detectors, etc.
• Know what percentage of US and world energy comes
  from nuclear material. Know the country that
  leads in nuclear usage.

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Extra

• Discovery Learning Video Chemistry Connections
  Nuclear Changes
• Radioactivity Homework