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Nuclear Chemsitry

VIEWS: 5 PAGES: 50

									Nuclear Chemistry
CHAPTER 10




             Intro Clip (2:40)
10.1 Radioactivity
 Radioactivity - when an unstable atomic
  nucleus emits charged particles and
  energy.
 Nuclear decay - atoms of 1 element can
  change into atoms of a different element.
Over100 mammoths died at a
sinkhole in Hot Springs, South
Dakota.




   Can you determine a way to calculate how old these
    once furry elephants might be?
Carbon-14 Dating
They are about 26,000 years old.




                                Mammoth Tooth


FYI: Ms. Lolich went here on a quick trip west.
                          Yes…….she is a science geek.
Nuclear radiation
   Charged particles & energy that are
    emitted from the nuclei of radioisotopes.
    ◦ Alpha
    ◦ Beta
    ◦ Gamma
Alpha Decay
   positively charged (+2)
   2 protons and 2 neutrons (like He but no e)
   symbol 42He or the Greek letter α.
   Low penetrating power
   Travel only a few cm. thru air.
   Does not pose a health hazard
What do those numbers mean?
Mass Number




Atomic Number
Example of Alpha Decay
 240     Pu   236     U + 42 He
    94           92
ASK MS. LOLICH FOR
HER WEIRD WAY TO
REMEMBER THIS……
Beta Decay
   Occurs when a neutron decomposes into a
    proton and an electron.
   negative charge
   no mass
   symbol 0−1e or the Greek letter β.
   100x more penetrating than the α particle.
   Can pass through clothing and damage skin.
   * assigned an atomic number of −1
Example of Beta Decay
228     Ra   228     Ac + 0-1 e
   88           89
             B “e”TA DECAY




ASK MS. LOLICH FOR
HER WEIRD WAY TO
REMEMBER THIS……
Gamma Decay
 Energetic form of light similar to X-ray
 Has no mass - does not affect atomic #
  or mass # (like an electron)
 Often occurs with α and β radiation
 no charge
 Greek symbol is γ
 Can travel through tissue and solid
  material - stopped by concrete and lead.
Example of Gamma Decay
240
   94   Pu   240
                94   Pu + γ radiation
Penetrating Powers of Nuclear
Radiation
Notice the red dotted line
Effects of Nuclear Radiation
Background radiation - naturally occurs
 in the environment.
 1.You’re exposed daily.
 2. Found in: air, water, rocks, plants, and
 animals, comic rays.
 3. Not harmful.
Effects of Nuclear Radiation

Once nuclear radiation
 exceeds background
 levels, it can damage
 the cells and tissues
 of your body.

David Hahn needs
 Proactive – NOT!
Detecting Nuclear Radiation

   Devices that are used to detect nuclear
    radiation include:
    ◦ Geiger counters
    ◦ Film badges.
10.2 Rates of Nuclear Decay
   A half-life is the time required for one
    half of a sample of a radioisotope to
    decay.




           Video Clip (1:24)
So how long does it take anyhow?
   Half-lives can vary
    ◦ fractions of a second
    ◦ billions of years.
   Nuclear decay rates are constant.
The half-life for iodine-131 is
8.07 days.
After one half-life (8.07 days), half of
a sample of iodine-131 will have
decayed into xenon-131.
After two half-lives (16.14 days),
three quarters of the sample will
have decayed.
After 3 half-lives (24.21 days), what
% will be remaining?
Half-lives of various Radioisotopes
Lab to follow
   Calculating Half-Life of Barium
    Students will observe radioactive decay and
    collect data from their Geiger counter to
    graph the half-life decay process.
10.3 Artificial Transmutation
 Transmutation - conversion of atoms of
  1 element to atoms of another.
 Involves a nuclear change, NOT a
  chemical change.




                 Video Clip (2:04)
Who’s your daddy daughter?
Natural all the way
 In natural transmutations, the nucleus
  decays spontaneously.
 There is only 1 reactant (or the nucleus)
  that undergoes the transformation.
 Alpha or beta particles are emitted.
So how do they do it artificially?
 Scientists bombard the atomic nuclei with
  high-energy particles such as protons,
  neutrons, or alpha particles.
 Particles are accelerated in accelerators,
  by using electric and magnetic fields.
Way to go Ernie!!
   In 1919, Ernest Rutherford bombarded
    nitrogen-14 with α particles.




   Notice the left side balanced with right.
You try….determine “X”?


                          4
                              He
                          2
One more time….Determine “X”?

                 30
                      P
                 15
10.4 Fission and Fusion
 P4.12d
 Identify the source of energy in fission and
  fusion nuclear reactions.




               Video Clip (FIRST 1:06 )
So what is nuclear force?
  Binds protons and
   neutrons together in
   the nucleus.
  Over very short
   distances its greater
   than the electric
   forces.

Remember + and + repel
but NOT with nuclear
force!!
Fission
 The splitting of an atomic nucleus into
  two smaller parts.
 Tremendous amounts of energy are
  produced from very small amounts of
  mass.
 This is how our nuclear reactor plants
  work.
Did you know?
   1 kilogram of uranium-235 is equal to the
    chemical energy produced by burning
    more than 17,000 kilograms of coal!
Nuclear Fission of Uranium-235
Nuclear Fission of Uranium-235
Nuclear Fission of Uranium-235
Nuclear Fission of Uranium-235
Real live “action” shots of Fission
What Ms. Lolich sees in her head


            ISSIO
           FISSION


            ISSO
          SCISSORS


  So Fission is like Scissors – right?
Fusion
 When the nuclei of 2 atoms
  combine to form a larger nucleus.
 Fusion also has a small fraction of the
  reactant mass that is converted into
  energy.
 This is how our sun works and reactor
  made in Junkyard Science article.
What do you need you ask?
 High temperatures.
 Plasma must exist.


   Plasma is a state of matter in which
    atoms have been stripped of their
    electrons.

Think of plasma (gas) = nuclei & electrons
Let’s break it down….
 …More like “stick it” together.
Something to consider as we end
our chapter.




   Video Clip (3:26)

								
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