nuclear chemistry. subatomic particles protons- plus charge in the nucleus neutrons- neutral...
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Nuclear chemistry
Subatomic Particles
• Protons- plus charge
In the nucleus• Neutrons- neutral
• Electrons - negative charge
Outside the nucleus
• http://www.teachersdomain.org/resources/phy03/sci/phys/energy/radsource/index.html
• http://www.teachersdomain.org/resources/tdc02/sci/life/evo/radiodating/index.html
• http://www.teachersdomain.org/resources/phy03/sci/phys/matter/date/index.html
• http://www.teachersdomain.org/resources/phy03/sci/phys/matter/threemile2/index.html
Stability of Nuclei
http://www.eas.asu.edu/~holbert/eee460/decay.html
• Ratio of neutrons to protons determines stability = “belt of stability”
• Ratio of nuclei with atomic numbers greater than 83 makes those nuclei unstable (radioactive, radioisotope)
• Unstable nucleus decays forming products that are more stable; emits radiation
Radiation
• Radiation comes from the nucleus of an atom.
• Unstable nucleus emits a particle or energy
alpha
gamma
beta
He42
Types of Radiation
• Alpha particle ()– helium nucleus paper2+
• Beta particle (-)– electron
e0-1
1-lead
• Positron (+)– positron
e01 1+
• Gamma ()– high-energy photon 0
concrete
Alpha Emission
He Th U 42
23490
23892
parentnuclide
daughternuclide
alphaparticle
Numbers must balance!!
Beta Emission
e Xe I 0-1
13154
13153
electronparentnuclide
daughternuclide
Numbers must balance!!
e Ar K 01
3818
3819
positron
Positron Emission
Numbers must balance!!
daughternuclide
parentnuclide
Balancing Nuclear Equations
1) Use Table N to determine decay mode
2) In the reactants and products…
Atomic and mass numbers must balance
3) A new element will be formed…
according to the new atomic number
DECAY MODE
Learning Check 1
What forms when carbon -14 decays?
Solution 1
What forms when carbon -14 decays?
14C 0 + 14 N
6 -1 7
Worksheet: Balancing nuclear equations
Half-Life of a Radioisotope
The time for the radiation level to fall (decay) to one-half its initial value
decay curve
8 mg 4 mg 2 mg 1 mg
initial
1 half-life 2 3
http://www.eas.asu.edu/~holbert/eee460/decay.html
Examples of Half-Life
Isotope Half life
C-15 2.4 sec
Ra-224 3.6 days
Ra-223 12 days
I-125 60 days
C-14 5700 years
U-235 710 000 000 years
HALF- LIFE
Learning Check 2
How many half lives will it take for 50 grams of 99 Tc to decay to 6.25 g?
½ life amount time
Solution 2
How many half lives will it take for 50 grams of 99 Tc to decay to 6.25 g? 3 half lives
½ life amount time0 50 01 25 2.13 x 105
2 12.5 2 (2.13 x 105)3 6.25 3 (2.13 x 105)
½ life amount time
Transmutation – One element becomes another.
Natural
Alpha
Beta
Gamma
Positron
Artificial
Fission
Fusion
Nuclear Fission
Fission
larger unstable nuclei break up into smaller more stable nuclei; release of neutrons causes a chain reaction and energy release
235U + 1n 139Ba + 94Kr + 3 1n +
92 0 56 36 0
Energy
Fission
Nuclear Power
• Fission Reactors Cooling Tower
Nuclear Power
• Fission Reactors
Nuclear Fusion
Fusion
small nuclei combine
2H + 3H 4He + 1n +
1 1 2 0
Occurs in the sun and other stars, hydrogen bomb
Energy
Nuclear Power
• Fusion Reactors (not yet sustainable)
Nuclear Power
• Fusion Reactors (not yet sustainable)
Tokamak Fusion Test Reactor
Princeton University
National Spherical Torus Experiment
Fission vs. Fusion
• 235U is limited• danger of
meltdown• toxic waste• thermal pollution
• fuel is abundant• no danger of
meltdown• no toxic waste• not yet sustainable
FISSION
FUSION
• 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
Nuclear Weapons
Learning Check 3
Indicate if each of the following are
(1) Fission (2) fusion
A. Nucleus splits
B. Large amounts of energy released
C. Small nuclei form larger nuclei
D. Hydrogen nuclei react
Energy
Solution 3
Indicate if each of the following are
(1) Fission (2) fusion
A. 1 Nucleus splits
B. 1 + 2 Large amounts of energy released
C. 2 Small nuclei form larger nuclei
D. 2 Hydrogen nuclei react
Nuclear Chemistry Uses
• Dating– dating previously living materials (Carbon-14) – dating rocks and other geological formations
(Uranium-238)
Nuclear Chemistry Uses
Medical Application
• Radiation Treatment– larger doses are used
to kill cancerous cells in targeted organs (Cobalt-60)
• Radioisotope Tracers (absorbed by specific organs and used to diagnose diseases)– Iodine-131 detection and treatment of thyroid conditions– Technetium-99 detects presence of tumors
Radiation treatment using-rays from cobalt-60.
Nuclear Chemistry Uses
• Food Irradiation radiation is used to kill bacteria (Co-60 and
Cs-137)
• Consumer Products– ionizing smoke detectors - 241Am
• Radioactive Tracers
(tracers follow the path of a material in a system) – Map the path of
carbon in metabolic processes
(Carbon-14)– study plant growth,
photosynthesis (Phosphorus-31)
Nuclear Chemistry Uses
Nuclear power plant.
Diagram for the tentative plan for
deep underground isolation of nuclear
waste.
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