Start Up21709

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Start Up 2/17/09

• What are the first three things that come to mind
  when hear the word NUCLEAR?

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Nuclear Chemistry
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Kentucky Core Content

• SC-HS-1.2.2
• Students will
• explain the relationship between electricity and
  magnetism
• propose solutions to real life problems
  involving electromagnetism. Electricity and
  magnetism are two aspects of a single
  electromagnetic force. Moving electric charges
  produce magnetic forces or fields and moving
  magnets produce electric forces or fields.
  This idea underlies the operation of electric
  motors and generators. DOK 3
• SC-H-MF-S-8
• Students will explain why the strength of the
  nuclear force is responsible for the great energy
  release involved in nuclear reactions
• SC-HS-1.2.3
• Students will understand that the electric force
  is a universal force that exists between any two
  charged objects. Opposite charges attract while
  like charges repel.

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Core Content TermsChapter 25

• Radioisotope
• Radioactivity
• Radiation
• Alpha particle
• Beta particle

• Gamma ray
• Half-life
• Fission
• Fusion
• Geiger counter

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Bookwork Reminder!

• Due Friday, February 20th!
• 4-THE ATOM and NUCLEAR CHEMISTRY
• Chapters 4 and 25
• Problems
• Chap. 4 4, 14, 25, 27, 28, 30, 32, 41, 50, 52,
  54
• Chap. 25 2, 3, 5, 13, 17, 28, 49, 58

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How bad is Nuclear Radiation?

• Fill out the side with the list of risks.
• Put them in order of most risky to least risky.
• On the back, determine your personal radiation
  dosage.

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How does the Atom stay together?

• Two major forces
• Strong Nuclear Force (like glue)
• Force between nucleons (protons neutrons)
• Holds the Nucleus together
• Electric Force (Electromagnetic)
• Force between nucleus and electrons
• Keeps electrons around nucleus

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A Brief History

• Henri Bequeral- French chemist, 1896
• discovered that uranium emitted radiation
• Pierre and Marie Curie-
• Marie- named emitted rays that caused fogging
  radioactivity
• All together won Nobel Prize in Physics in 1903

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Marie Curie

• Radiation-proportional to amount of radioactive
  element present

radiation was a property of atoms (not compounds)
1st woman to win a Nobel prize and the 1st
person to win TWO
-1st shared with Pierre and Becquerel for
discovering radioactivity -2nd for discovering
radium and polonium
Radiation-wave energy from any power
source Radioactivity energy emitted from
decaying atoms
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Where does Radiation come from?

• Due to instability of atoms
• Many isotopes especially the big atoms (all
  over 84) are unstable.
• Nucleus breaks into smaller parts emitting ?
  particles, ? particles and ? rays (Radioactive
  decay)
• Called Radioisotopes atoms of an element that
  produce nuclear radiation (radioactive)

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Recall Isotopes

• Same number of _________,
• but different number of_________.

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Radioactivity

• Spontaneous
• Decay will happen regardless of any environmental
  influences
• (You can heat the substance up, or subject it to
  high pressure or strong magnetic fields - in
  fact, do whatever you like to it - and you won't
  affect the rate of decay in the slightest)

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Radioactivity

• During radioactive decay, atoms of one element
  are changed into atoms of a different element
• For one element to change into another
• of protons in the nucleus must change
• Nuclear changes described using nuclear equations
• Atomic numbers and mass numbers are conserved!

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Three ways a nucleus decays It may give
out- an alpha particle, we use the symbol ? a
beta particle symbol ? a gamma ray symbol ?
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Alpha decay

• ? particle
• Use He or ? symbol
• Loss of an alpha particle means
• atomic number ? by 2
• mass number ? by 4

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Alpha Decay
alpha particle
radioactive isotope
neutron proton
Timberlake, Chemistry 7th Edition, page 87
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(No Transcript)
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You try

• Write a nuclear equation to represent the
  following
• Po 210 undergoes alpha emission.

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Beta Decay

• particle is like an electron
• Loss of a ? particle means
• atomic number ? by 1
• mass number remains the same
• Neutron changes into a proton

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Beta Decay
Timberlake, Chemistry 7th Edition, page 90
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You try

• Write a nuclear equation to represent the
  following
• C 14 emits a beta particle.

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Gamma emission

• Gamma (?) rays are high energy photons
• Occurs when the nucleus rearranges
• No loss of particles from the nucleus
• No change in the composition of the nucleus
• Same atomic number and mass number

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? Emission
Gamma rays (? ) are electromagnetic waves
-Thus gamma rays have no mass and no charge. 00?
218 84
218 84
?
0 0
Po
Po

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Positron emission

• Positron has a charge of 1 and negligible mass
• anti-electron
• Loss of a positron from the nucleus means
• mass number remains the same
• atomic number ? by 1
• positrons appear to result from a proton changing
  into a neutron

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You try

• Write a nuclear equation to represent the
  following
• Potassium 38 undergoes positron decay.

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Electron Capture

• An inner electron is pulled into the nucleus
• No particle emission, but atom changes
• same result as positron emission
• Proton combines with the electron to make a
  neutron
• mass number stays the same
• atomic number ? by one

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You try

• Write a nuclear equation to represent the
  following
• Silver 107 captures an electron.

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Start Up 2/18/09

• What causes nuclear radiation?
• What is the difference between radioactivity and
  radiation?
• 3. Write a nuclear equation for the following
  situation
• At-212 undergoes both alpha decay and gamma
  emission.

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Artificial Nuclear Transmutation

• Changing one element into another by bombarding
  it with small nuclei, protons, or neutrons
• Done in a particle accelerator
• man-made transuranium elements

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Unstable Nucleus
Zumdahl, Zumdahl, DeCoste, World of Chemistry
2002, page 620
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Characteristics of Some Ionizing Radiations
Property Alpha radiation
Beta radiation Gamma radiation
Alpha particle (helium nucleus)
Beta particle (electron)
High-energy electro- magnetic radiation
Composition
a, He-4
b, e
g
Symbol
1-
Charge
2
0
4 (biggest)
1/1837 (medium)
0 (smallest)
Mass (amu)
Carbon-14
Common source
Radium-226
Cobalt-60
0.05 to 1 MeV
Approximate energy
5 MeV
1 MeV
Moderate (4 mm body tissue)
Very high (penetrates body easily)
Penetrating power
Low (0.05 mm body tissue)
Metal foil
Shielding
Paper, clothing
Lead, concrete
(1 MeV (millelectron volt) 1.60 x 10-13 J)
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Absorption of Radiation
Timberlake, Chemistry 7th Edition, page 84
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Radioactive Dating

• Means of measuring the age of material by
  comparing the amount of a radioisotope in a
  fossil with the amount of its decay product
• Each radioactive element decays at a different
  rate

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Dating fossils

• C-14 dating is only used on fossils that are less
  than 50,000 years old
• Older fossils or rocks are dated using the
  following radioactive elements thorium-232,
  uranium-235, or potassium-40

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(No Transcript)
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Half-life

• Scientists use the half-life of a radioactive
  element to date rocks and fossils
• Amount of time required for one-half of the
  radioactive form of the element to change into
  its decay product.

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Half-life

• Half-life (t½)
• Time required for half the atoms of a radioactive
  nuclide to decay.
• Shorter half-life less stable.

1/1
Newly formed rock
Potassium
Argon
Calcium
Ratio of Remaining Potassium-40 Atoms to
Original Potassium-40 Atoms
1/2
1/4
1/8
1/16
0
1 half-life 1.3
1 half-lives 2.6
3 half-lives 3.9
1 half-lives 5.2
0
Time (billions of years)
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Half-life
1.00 mg


0.500 mg
0.500 mg

131 53
I
0.250 mg
0.250 mg
0.125 mg
8.02 days
16.04 days
24.06 days
0.00 days
Dorin, Demmin, Gabel, Chemistry The Study of
Matter 3rd Edition, page 757
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Half-life Equation
A(t) A0 (1/2)t/h A0 starting amount of
substance t time h half-life Complicated!!!
So, instead use logic!
Courtesy Christy Johannesson www.nisd.net/communic
ationsarts/pages/chem
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Example of half-life problem

• Carbon-14 is a radioactive form of carbon that
  has a half-life of 5,730 years.
• If you start out with 20 grams of Carbon-14, how
  many years will it take to reach 5 grams of
  carbon-14?

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Example 2

• The half-life of thorium-234 is 24 days. If a
  piece of wood contained 16 grams of thorium-234
  at the time it was cut, how many grams of
  thorium-234 will be present in the wood 96 days
  later?

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Changes

• More practice today.
• Review for test tomorrow.

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Uses of Nuclear Chemistry

• Radioisotopes, Fission, and Fusion

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Nuclear Weapons

• Atomic Bomb
• chemical explosion is used to form a critical
  mass of 235U or 239Pu
• fission develops into an uncontrolled chain
  reaction
• Hydrogen Bomb
• chemical explosion ? fission ? fusion
• fusion increases the fission rate
• more powerful than the atomic bomb

Courtesy Christy Johannesson www.nisd.net/communic
ationsarts/pages/chem
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Atoms for Peace

• Eisenhower
• Show nuclear science is not evil
• Has good uses, too.
• Power
• Food irradiation
• Cancer treatment
• Cancer/disease diagnosis (Radiotracers)
• PET CAT scan
• Destroy ANTHRAX bacteria

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Medical Uses of Radioisotopes

• Radiotracers
• certain organs absorb most or all of a particular
  element
• can measure the amount absorbed by using tagged
  isotopes of the element and a Geiger counter
• use radioisotope with short half-life and
  non-toxic

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Nuclear Power Plants
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How does nuclear power work?

• Fission-Chain Reaction
• Chain reaction occurs when a reactant is also a
  product
• in the fission process -neutrons
• only need a small amount of neutrons to keep the
  chain going

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Stages of Fission
First stage 1 fission Second stage 2
fissions Third stage 4 fissions
Kelter, Carr, Scott, Chemistry A World of Choices
1999, page 454
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Inside a nuclear power plant.
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Nuclear Fusion
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Nuclear Power
Fusion Reactors (not yet sustainable)
National Spherical Torus Experiment
Tokamak Fusion Test Reactor Princeton University
Courtesy Christy Johannesson www.nisd.net/communic
ationsarts/pages/chem
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Notebook Quiz 9/19/08

• Write your whole answer to the start up from
  2/7/08.
• Use your CCT, to define the word isotope.
• Write your whole answer to the start up from
  2/11/08.
• Write your whole answer to the start up from
  2/15/08.
• Write your whole answer to the start up from
  2/19/08.
• Use your CCT to define radiation.

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Start Up-Review of old stuff 2/19/09

• What is the difference between an isotope and an
  ion? Give an example of each.
• Who is known for developing the atomic theory?
• Who discovered the nucleus?

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Today

• Half-life Activity
• Review
• Bookwork.any questions?
• Concept Map?

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Activity Concept Map

• Use at least all of your CCT from atomic and
  nuclear chapters to create a map
• Who can get the most? (individual elements not
  permitted.)
• Map must make sense!

Atom
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Sources

• Mrs. Jennifer Carter
• Mr. Dan Martin
• Mrs. Kristen Olsen
• Introductory Chemistry A Foundation(Steven S.
  Zumdahl)
• Thanks!!

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Start Up 2/20/09

• Explain the difference between fusion and
  fission.
• Old Stuff
• Write the atomic number, atomic mass, p, n, e
  for sulfur.
• Write a complete chemical symbol for a Silicon
  ion with a charge of -2.