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Nuclear Nuclear ChemistryChemistryChapter 25Chapter 25
2Nuclear Chemistry Nuclear Chemistry
UsesUses
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RadioactivityRadioactivity
• One of the pieces of evidence for the One of the pieces of evidence for the fact that atoms are made of smaller fact that atoms are made of smaller particles came from the work ofparticles came from the work of
________ ________ (1876-1934).(1876-1934). • She discoveredShe discovered ________________, the , the
spontaneous disintegration of some spontaneous disintegration of some elements into smaller pieces.elements into smaller pieces.
radioactivityradioactivity
Marie CurieMarie Curie
4Band of Stability Band of Stability and Radioactive and Radioactive DecayDecay
5Nuclear Reactions vs. Nuclear Reactions vs. Normal Chemical Normal Chemical
ChangesChanges• Nuclear reactions involve the Nuclear reactions involve the __________________• The nucleus opens, and the The nucleus opens, and the
____________________________________________are rearrangedare rearranged• The opening of the nucleus releases a The opening of the nucleus releases a
tremendous amount of energy that holds tremendous amount of energy that holds the nucleus together – called the nucleus together – called __________________________________
• ““Normal” Chemical Reactions involve, Normal” Chemical Reactions involve, ________________________ not protons and neutrons not protons and neutrons
nucleusnucleus
protons and neutronsprotons and neutrons
binding energybinding energy
electronselectrons
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Mass DefectMass Defect
• Some of the mass can be converted into Some of the mass can be converted into energyenergy
• Shown by a very famous equation!Shown by a very famous equation!
E=mcE=mc22
EnergyEnergy
MassMass
Speed of lightSpeed of light
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Types of RadiationTypes of Radiation
e01
He42
•___________– a positively ___________– a positively charged helium isotopecharged helium isotope - - we we usually ignore the charge because it involves usually ignore the charge because it involves electrons, not protons and neutronselectrons, not protons and neutrons
•Beta (Beta (ββ) – _______________) – _______________
•___________– pure energy; ___________– pure energy; called a ray rather than a called a ray rather than a particleparticle
00
Gamma (Gamma (γγ))
electronelectron
Alpha (Alpha (άά))
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Other Nuclear ParticlesOther Nuclear Particles
e01
n10• ____________________________
• ___________ – a positive ___________ – a positive electronelectron
•Proton – usually referred to Proton – usually referred to as hydrogen-1as hydrogen-1
•Any other elemental isotopeAny other elemental isotope
H11
NeutronNeutron
PositronPositron
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Geiger Counter
• Used to detect ____________________Radioactive substancesRadioactive substances
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Penetrating AbilityPenetrating Ability
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Balancing Nuclear ReactionsBalancing Nuclear Reactions•In the ____________ (starting materials – on the left side of an equation) and _______ (final products – on the right side of an equation)
Atomic numbers must balanceand
Mass numbers must balance
Use a particle or isotope to fill in the missing protons and neutrons
productsproducts
reactantsreactants
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Nuclear ReactionsNuclear Reactions• Alpha emissionAlpha emission
Note that mass number (A) goes _________ and atomic number (Z) goes _____________
_____________ (nuclear particles… protons and neutrons) are rearranged but conserved
Down by 2Down by 2
Down by 4Down by 4
NucleonsNucleons
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Nuclear ReactionsNuclear Reactions• Beta emissionBeta emission
Note that mass number (A) is ___________ and atomic number (Z) ______________Goes up by 1Goes up by 1
unchangedunchanged
14Other Types of Nuclear Other Types of Nuclear ReactionsReactions
Positron (Positron (00+1+1): a positive electron): a positive electron
Electron capture: Electron capture: the capture of an electron
207 207
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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.
17Uranium-238 Decay Uranium-238 Decay SeriesSeries
18Artificial Nuclear Artificial Nuclear ReactionsReactions
New elements or new isotopes of known elements New elements or new isotopes of known elements are produced by bombarding an atom with a are produced by bombarding an atom with a subatomic particle such as a proton or neutron -- subatomic particle such as a proton or neutron -- or even a much heavier particle such as or even a much heavier particle such as 44He and He and 1111B.B.
Reactions using _____________ are called Reactions using _____________ are called
reactions reactions because a because a ray is usually ray is usually emitted.emitted.
_________________used in medicine are often _________________used in medicine are often made by made by reactions. reactions.
neutrons neutrons
RadioisotopesRadioisotopes
19Artificial Nuclear Artificial Nuclear ReactionsReactions
(Transmutations)(Transmutations)
Example of a Example of a reaction reaction is production is production
of radioactive of radioactive 3232P for use in studies of P P for use in studies of P
uptake in the body.uptake in the body.
31311515P + P + 11
00n --->n ---> 32321515P + P +
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Transuranium ElementsTransuranium Elements
Elements beyond 92 Elements beyond 92 (transuranium)(transuranium) made made
starting with an starting with an reaction reaction
2382389292U + U + 11
00n --->n --->
---> ---> 2392399393Np + Np + 00
-1-1
2392399393Np Np --->--->
2392399292U + U +
2392399494Pu + Pu + 00
-1-1
2392399292UU
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Nuclear Fission
• http://www1.teachertube.com/members/viewVideo.php?video_id=173394
• http://www.youtube.com/watch?v=JxzPN-vdP_0
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Nuclear FissionNuclear Fission
23Representation of a fission process.
24Nuclear Fission & Nuclear Fission & POWERPOWER
• Currently about 103 Currently about 103
nuclear power plants in nuclear power plants in
the U.S. and about 435 the U.S. and about 435
worldwide.worldwide.
• 17% of the world’s 17% of the world’s
energy comes from energy comes from
nuclear.nuclear.
25Figure 19.6: Diagram of a nuclear power plant.
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Nuclear Fusion
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Nuclear Fusion
Fusion __________________
2H + 3H 4He + 1n +
1 1 2 0
Occurs in the ____________________
Energy
small nuclei combinesmall nuclei combine
sun and other starssun and other stars
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Nuclear Fusion
Fusion
• Excessive heat can not be contained
• Attempts at “cold” fusion have ______________
• “Hot” fusion is difficult to containFailedFailed
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Half-LifeHalf-Life
•HALF-LIFEHALF-LIFE is the time that it takes for is the time that it takes for ____________________________________________________________
• The rate of a nuclear transformation The rate of a nuclear transformation depends only on the “reactant” depends only on the “reactant” concentration.concentration.
1/2 a sample to decompose1/2 a sample to decompose
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Half-LifeHalf-Life
Decay of 20.0 mg of Decay of 20.0 mg of 1515O. What remains after 3 half-lives? O. What remains after 3 half-lives? After 5 half-lives?After 5 half-lives?
31Kinetics of Radioactive Kinetics of Radioactive DecayDecay
For each duration (half-life), one half of the substance
decomposes.
For example: Ra-234 has a half-life of 3.6 days
If you start with 50 grams of Ra-234
After 3.6 days > __________After 3.6 days > __________
After 7.2 days >___________After 7.2 days >___________
After 10.8 days > _________After 10.8 days > _________
25 grams25 grams
12.5 grams12.5 grams
6.25 grams6.25 grams
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Learning Check!
The half life of I-123 is 13 hr. How much of a 64 mg sample of I-123 is left after 39 hours?
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Effects of RadiationEffects of Radiation
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Radiocarbon DatingRadiocarbon DatingRadioactive C-14 is formed in the upper atmosphere Radioactive C-14 is formed in the upper atmosphere
by nuclear reactions initiated by neutrons in cosmic by nuclear reactions initiated by neutrons in cosmic radiationradiation
1414N + N + 11oon ---> n ---> 1414C + C + 11HH
The C-14 is oxidized to COThe C-14 is oxidized to CO22, which circulates through , which circulates through
the biosphere.the biosphere.
When a plant dies, the C-14 is not replenished.When a plant dies, the C-14 is not replenished.
But the C-14 continues to decay with tBut the C-14 continues to decay with t1/21/2 = 5730 years. = 5730 years.
Activity of a sample can be used to date the sample.Activity of a sample can be used to date the sample.
36Nuclear Medicine: Nuclear Medicine: ImagingImaging
Thyroid imaging using Tc-99mThyroid imaging using Tc-99mCT BONE SCANCT BONE SCAN
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Radioactive Tracing(Using oxygen-18)
• http://www.ausetute.com.au/esters.html
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Food Food IrradiationIrradiation
•Food can be irradiated with ______ from Food can be irradiated with ______ from 6060Co or Co or 137137Cs.Cs.•Irradiated milk has a shelf life of 3 mo. Irradiated milk has a shelf life of 3 mo.
without refrigeration.without refrigeration.•USDA has approved irradiation of meats USDA has approved irradiation of meats
and eggs.and eggs.
rays rays
