Title: Nuclear Chemistry
1Nuclear Chemistry
2Nuclear Chemistry
- Nuclear Chemistry- the study of reactions
involving changes in atomic nuclei. - Importance
- Disadvantages
3Nuclear Reactions
- Except for Hydrogen, all nuclei contain particles
called protons and neutrons. - Nuclei can be stable or unstable.
- Unstable Nuclei emit particles and/or
electromagnetic radiation spontaneously. - Phenomenon is called Radioactivity.
- Nuclear Transmutation- results from the
bombardment of nuclei by neutrons, protons or
other nuclei.
4Nuclear Reactions
- Atomic number (Z) number of protons in nucleus
- Mass number (A) number of protons number of
neutrons - atomic number (Z) number
of neutrons
5Nuclear Reactions
6Balancing Nuclear Equations
- Conserve mass number (A).
The sum of protons plus neutrons in the products
must equal the sum of protons plus neutrons in
the reactants.
235 1 138 96 2x1
7Balancing Nuclear Equations
- Conserve atomic number (Z) or nuclear charge.
The sum of nuclear charges in the products must
equal the sum of nuclear charges in the reactants.
92 0 55 37 2x0
8Balancing Nuclear Equations
212Po decays by alpha emission. Write the
balanced nuclear equation for the decay of 212Po.
212 4 A
A 208
Z 82
84 2 Z
23.1
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10Chemical Reactions vs. Nuclear Reactions
11Nuclear Stability
- Nucleus is very small
- Contributes most of weight of atom
- Extremely high density
- Even higher of particles
12Nuclear Stability
- Particles repel/attract each other
- neutron-to-proton ratio
- Predicting stability
- Magic numbers 2,8,20,50,82,126
- Even numbers of neutrons and protons vs. odd
numbers - All isotopes of elements with atomic numbers
higher than 83 are radioactive. - All isotopes of Tc and Pm are radioactive.
13n/p too large
beta decay
n/p too small
positron decay or electron capture
14Nuclear Stability
Beta decay
Decrease of neutrons by 1
Increase of protons by 1
23.2
15Nuclear Stability
Positron decay
Increase of neutrons by 1
Decrease of protons by 1
16Nuclear Stability
Electron capture decay
Increase of neutrons by 1
Decrease of protons by 1
17Nuclear Stability
Alpha decay
Decrease of neutrons by 2
Decrease of protons by 2
18Nuclear Binding Energy
- Nuclear Binding Energy- the energy required to
break up a nucleus into its component protons and
neutrons. - Necessity?
- Mass Defect
- Einsteins Theory of Relativity
E mc2
19Nuclear Binding Energy
E mc2
BE 9 x (p mass) 10 x (n mass) 19F mass
BE (amu) (9 x 1.007825) (10 x 1.008665)
18.9984
BE 0.1587 amu
1 amu 1.49 x 10-10 J
BE 2.37 x 10-11J
20Nuclear Binding Energy
1.25 x 10-12 J
21Nuclear Binding Energy
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24Natural Radioactivity
- Outside the belt of stability, nuclei are
radioactive. - Radioactive nuclei spontaneously emit radiation.
- a particles, ß particles, ? rays, etc.
- Disintegration of radioactive nucleus leads
- to a decay series.
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26Radioactive Decay--Dating
- Uranium decay
- After time, half of parent exsists
- Equal amounts of parent and daughter
- Age?
27Nuclear Transmutations
- Rutherford, 1919
- Artificial Radioactivity
- Nitrogen bombarded by a particles
28Nuclear Transmutation
- Notation for reactions
- First Isotope (bombarding particle, ejected
particle) Final Isotope - Notation for Nitrogen-14 bombarded with a
particle.
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30Transuranium Elements
- Synthetic elements
- Atomic Numbers greater than 92
- Particle Accelerator necessary for preparation
31Particle Accelerator
32Nuclear Fission
- Nuclear Fission- the process in which a heavy
nucleus (mass number gt 200) divides to form
smaller nuclei of intermediate mass and one or
more neutrons. - Energy is released.
- Uranium-235 was the first element discovered to
go through nuclear fission.
33Nuclear Fission
34Nuclear Fission
- Nuclear chain reaction is a self-sustaining
sequence of nuclear fission reactions.
The minimum mass of fissionable material required
to generate a self-sustaining nuclear chain
reaction is the critical mass.
35Chain Reaction
36The Atomic Bomb
37Nuclear Reactors
- Peaceful application of nuclear fission
- Generates electricity from chain reactions
- Provides 20 of electricity in U.S.
- Light water reactors Heavy water reactors
Breeder reactors
38Light Water Reactors
- Most U.S. nuclear reactors are light water
- Light Hydrogen
- Use Uranium-235 under controlled conditions
- Releases large quantities of steam
- Steam drives electric generators
- Needs large amounts of coolant
- Plants built by lakes and rivers
- Large amounts of thermal pollutant
39Light Water Reactors
40Heavy Water Reactors
- Uses Deuterium D2O
- D absorbs neutrons less efficiently than H
- Does not require U-235
- Neutrons leak out of reactor
- Expensive to prepare D2O
- Environmentally friendly
41Breeder Reactors
- Breeder Reactor- uses uranium fuel, but unlike a
conventional nuclear reactor, it produces more
fissionable materials than it uses. - Converts uranium-238 to plutonium-239 in a 3 step
process. - Plutonium-239 undergoes fission
- Reactor produces 1 mole of p-239 for every 1 mole
used. - Takes 7-10 years for complete regeneration.
42Hazards of Nuclear Energy
- Production of radioactive isotopes with long
half-lives (24,400 years) - Radioactive and toxic substances
- Three-mile Island Reactor- radiation escaped
- Chernobyl Nuclear Plant- fire and explosion
- Accidents
- Waste Disposal
43Nuclear Fusion
- Nuclear Fusion- the combining of small nuclei
into larger ones. - Two small nuclei can combine and release large
amounts of energy - To occur, the nuclei must be in an environment
with high temperature. - Thermonuclear Reactions
- Nuclear fusion occurs constantly on the Sun.
44Nuclear Fusion
- How do we get it to occur?
- Container?
45The Hydrogen Bomb
- Thermonuclear Bomb
- All power and no control
- Fusion reaction then fission reaction
- Fusion reaction creates high temp. for fission
reaction - Bombs usually contain Co-59 and upon explosion
convert to Co-60