CHAPTER 25 Nuclear Chemistry
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Transcript of CHAPTER 25 Nuclear Chemistry
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CHAPTER 25
Nuclear
Chemistry
CHAPTER 25
Nuclear
ChemistryI. The Nucleus -I. The Nucleus -
TermsTerms(p. 798-820)
I. The Nucleus -I. The Nucleus -TermsTerms
(p. 798-820)
I
IV
III
II
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Ionizing RadiationIonizing RadiationIonizing RadiationIonizing Radiation
Radiation is a form of energy transferred by waves or atomic particles
Ionizing Radiation is any radiation with high enough energy to create ions (by knocking electrons out of atoms)like UV, X, gamma, and cosmic rays
There are both natural sources of radiation (unstable nuclei and stars) and human created sources
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Zone of StabilityZone of StabilityZone of StabilityZone of Stability
Stable nuclei exist within the “zone of stability” seen on the graph…not always a 1:1 ratio of p+ to no
Outside this range, nuclei are unstable and will decay (disintegrate) into new nuclei
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DefinitionsDefinitionsDefinitionsDefinitions
Nucleons = particles in nucleus (p+ and n0)Nuclide refers to the nucleus of an atomNuclear Reactions involve transmutation
where one element become another. Radioactive Decay is the when unstable
nuclei spontaneous lose energy by emitting ionizing particles; as this changes the nucleus of the atom, this also changes the type of element
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Alpha Particle(Helium Nucleus)(4.00147 amu)
Alpha Decay ProcessAlpha Decay ProcessAlpha Decay ProcessAlpha Decay Process
Parent NuclideAm-241U-238Th-232Ra-226
Daughter NuclideNp-237Th-234Ra-228Rn-222
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A. Mass DefectA. Mass DefectA. Mass DefectA. Mass Defect
The mass defect describes the mass lost during the formation of nuclei
Difference between the mass of an atom and the mass of its individual particles.
4.00260 amuMass of atom
4.03298 amuMass of particles
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B. Nuclear Binding B. Nuclear Binding EnergyEnergy
B. Nuclear Binding B. Nuclear Binding EnergyEnergy
Energy released when a nucleus is formed from nucleons. This contributes to the loss in mass of nucleus, described by E = mc2.
High binding energy = stable nucleus.
E = mc2E: energy (J)m: mass defect (kg)c: speed of light
(3.00×108 m/s)
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B. Nuclear Binding B. Nuclear Binding EnergyEnergy
B. Nuclear Binding B. Nuclear Binding EnergyEnergy
Unstable nuclides are radioactive and undergo radioactive decay.
Iron (Fe) is the most stable nucleus!!
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CHAPTER 25
Nuclear
Chemistry
CHAPTER 25
Nuclear
ChemistryII. Radioactive II. Radioactive
DecayDecay(p. 798-820)
II. Radioactive II. Radioactive DecayDecay
(p. 798-820)
I
IV
III
II
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He42
Types of Spontaneous Types of Spontaneous RadiationRadiation
Types of Spontaneous Types of Spontaneous RadiationRadiation
Alpha particle () helium nucleus paper2+
Beta particle or - electron
e0-1 1-
woodPositron +
positrone0
1 1+
Gamma () high-energy photon 0
Lead orconcrete
Greek symbol charge
stopped by…
γ00
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p11
Other Radiation particlesOther Radiation particlesOther Radiation particlesOther Radiation particles
proton p++1
neutron n0
n10 0
Greek symbol charge
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How does an electron get How does an electron get emitted from the nucleus?emitted from the nucleus?How does an electron get How does an electron get emitted from the nucleus?emitted from the nucleus?
Basically a neutron splits into a proton which stays in the nucleus and an electron is emitted ( decay)
n & p in nucleus
n is “really” like a p and e together
n converted to a proton and an e is emitted
+ ++ +
+-
-
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Transmutation ReactionsTransmutation ReactionsTransmutation ReactionsTransmutation Reactions
I Alpha Emission
He Th U 42
23490
23892
parentnuclide
daughternuclide
alphaparticle
Numbers must balance on both sides of arrow!!238amu on left = (234 + 4amu)
92 is nucl chrg on left = 90 + 2 on right
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B. Nuclear DecayB. Nuclear DecayB. Nuclear DecayB. Nuclear Decay
II Beta Emission
e Xe I 0-1
13154
13153
electron III Positron Emission
e Ar K 01
3818
3819
positron*a proton 1p is not the same as a positron 0e
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B. Nuclear DecayB. Nuclear DecayB. Nuclear DecayB. Nuclear Decay
IV Electron Capture
Pd e Ag 10646
0-1
10647
electron
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B. Nuclear DecayB. Nuclear DecayB. Nuclear DecayB. Nuclear Decay
V Alpha Capture followed by neutron emission
n Cl He P 10
3417
42
3115
Alpha captureGamma Emission causes no change in mass or charge and…
Usually follows the previous
types of decay.
γ00
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Beta (Negatron) Decay ProcessBeta (Negatron) Decay ProcessBeta (Negatron) Decay ProcessBeta (Negatron) Decay Process
Parent NucleusRhenium-187Potassium-40
Daughter NucleusOsmium-187Calcium-40
Beta Particle(electron)
Antineutrino
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Beta ParticlesBeta ParticlesBeta ParticlesBeta Particles
Same as an electron with kinetic energyPositive or negative charge of 1May be positively or negatively chargedCan normally be stopped by 1 cm of
plastic, wood, paper Exception for positron emitters
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B. Nuclear DecayB. Nuclear DecayB. Nuclear DecayB. Nuclear Decay
Why nuclides decay…pg. 803 need stable ratio of neutrons to protons
He Th U 42
23490
23892
e Xe I 0-1
13154
13153
e Ar K 01
3818
3819
Pd e Ag 10646
0-1
10647
DECAY SERIES TRANSPARENCY
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C. Half-lifeC. Half-lifeC. Half-lifeC. Half-life
Half-life (t½) Time required for half the atoms of a
radioactive nuclide to decay. Shorter half-life = less stable.
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C. Half-lifeC. Half-lifeC. Half-lifeC. Half-life
nif mm )( 2
1
mf: final massmi: initial massn: # of half-lives
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C. Half-lifeC. Half-lifeC. Half-lifeC. Half-life Fluorine-21 has a half-life of 5.0 seconds. If you start
with 25 g of fluorine-21, how many grams would remain after 60.0 s?
GIVEN:
t½ = 5.0 s
mi = 25 g
mf = ?
total time = 60.0 s
n = 60.0s ÷ 5.0s =12
WORK:
mf = mi (½)n
mf = (25 g)(0.5)12
mf = 0.0061 g
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Decay SeriesDecay SeriesDecay SeriesDecay Series Many heavy elements Many heavy elements
are unstable and so are unstable and so they will continue to they will continue to decay (be radioactive) decay (be radioactive) until they finally until they finally transmute into a transmute into a stable nucleus.stable nucleus.
Here is an example of Here is an example of the Th-232 decay the Th-232 decay seriesseries
Thorium oxide is used Thorium oxide is used to in camping lanterns to in camping lanterns to intensify the to intensify the brightness when on brightness when on fire. fire.
Stable isotope