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Nuclear Reactions. Natural Transmutation. 1 term on reactant side Original isotope 2 terms on product side Emitted Particle New Isotope. Happens all by itself (spontaneous) Not affected by anything in environment. 8. -1. Natural Transmutation. 16 N 0 e + 16 O. 7. - PowerPoint PPT Presentation
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Nuclear ReactionsNuclear Reactions
Natural Transmutation1 term on reactant side
Original isotope
2 terms on product sideEmitted Particle New Isotope
Happens all by itself (spontaneous)Happens all by itself (spontaneous)Not affected by Not affected by anythinganything in environment in environment
Natural Transmutation
16N 0e + 16O7 -1 8
1 term on reactant side
2 terms on product side
Artificial Transmutation• Cause it to happen by smashing
particles into one another
• 2 terms on reactant side• Original Isotope• Particle that hits it
–neutron, proton, or -particle
• Product side: usually 2 terms
Artificial Transmutation
27Al + 4He 30P + 1n13 2 15 0
Original isotope or target nucleus
“Bullet”-what hits isotope
Artificial Transmutation27Al + 4He 30P + 1n1313 22 1515 00
1414N + N + 44He He 1717O + O + 11HH77 22 88 11
7575As + As + 44He He 7878Br + Br + 11nn3333 22 3535 00
3737Cl + Cl + 11n n 3838ClCl1717 00 17
All of these equations have 2 reactants!
Bombarding with Protons or
Protons and -particles have positive charge and mass • do some damage when hit target nucleus• must be accelerated to high speeds to overcome
repulsive forces between nucleus & particle (both are +)
What is an accelerator?• vacuum chamber (usually a long pipe)
– surrounded by vacuum pumps, magnets, radio-frequency cavities, high voltage instruments and electronic circuits
• inside the pipe particles are accelerated to very high speeds then smashed into each other
Fission ReactionFission Reaction SSplitting heavy nucleus into 2 lighter plitting heavy nucleus into 2 lighter nucleinuclei
Requires a critical mass of fissionable isotopeRequires a critical mass of fissionable isotopeControlled – nuclear reactorControlled – nuclear reactorUncontrolled – bombUncontrolled – bomb
FissionReactant side: 2 terms
• 1 heavy isotope (examples: U-235 or Pu-239)• Bombarding particle – usually a neutron
• Product side: at least 2 terms• 2 medium-weight isotopes• 1 or more neutrons• Huge amount of energy is released
• Fission = Division
Fission235U + 1n 91Kr + 142Ba + 31n + energy
9292 00 3636 5656 00
235235U + U + 11n n 7272Zn + Zn + 160160Sm + 4Sm + 411n + energyn + energy9292 00 3030 006262
More than 200 different product More than 200 different product isotopes identified from fission of U-235 isotopes identified from fission of U-235
A small amount of mass is converted to A small amount of mass is converted to energy according to E = mcenergy according to E = mc22
Fission Chain ReactionFission Chain Reaction
Fusion• Reactant side has 2 small nuclei:
– H + H; H + He; He + He• Product side:
– 1 nucleus (still small) and maybe a particle• Source of sun’s energy• 2 nuclei unite
2H + 3H 4He + 1n + energy11 11 22 00
CERN
•Particles travel just below speed of light
•In 10 hrs: particles make 400 million revolutions of the ring
27 kilometer ring
FermiLab
4 miles in circumference!
Balancing Nuclear Equations
Nuclear Equations - tasks
• Identify type (4 types)
• Balance to find 1 unknown term
Natural Transmutation – ID
• 1 term on reactant side – starting isotope
• 2 terms on product side – ending isotope and emitted particle
• Type of particle emitted characteristic of isotope – Table N
Nuclear Equations
• To balance: use conservation of both atomic number & mass number
• Mass number = left superscript
• Atomic Number = left subscript
Balancing Nuclear Equations
16N 0e + 16O7 -1 8
Conservation of mass number: 16 = 0 + 16Conservation of atomic
number: 7 = -1 + 8
Writing Equations• Write the equation for the decay of
Thorium-232• Use Table N to find the decay mode:
α• Write the initial equation: 232Th 4He + X
figure out figure out what element what element it turned intoit turned into
9090 2
Write an equation for the α decay of Am-241
241 Am 4He + YX What’s X?
95 2 Z
232Th 4He + X9090 22
Conservation of Mass Number:Conservation of Mass Number:
sum of mass numbers on left side must = sum of mass numbers on left side must = sum of mass numbers on right sidesum of mass numbers on right side
YY
Z
232 = 4 + Y so Y = 228
232Th 4He + 228X9090 22
Conservation of Atomic Number:Conservation of Atomic Number:
sum of atomic numbers on left side must = sum of atomic numbers on left side must = sum of atomic numbers on right sidesum of atomic numbers on right side
ZZ
90 = 2 + Z so Z = 88
232Th 4He + 228X90 2 88
Use the PT to find X: X = Ra
232232Th Th 44He + He + 228228RaRa90 2 88
Alpha (α) decay:233U 229Th + 4He 92 90 2
232Th 228Ra + 4He 90 88 2
175Pt 171Os + 4He 78 76 2
How does the mass number or atomic number change in α,β or γ
decay?• go to Table N:
– find isotope that decays by alpha or β decay– write the equation– see how the mass number (or atomic number)
changes• 226
88Ra 42 + X so X has to be 222
86X
• X is Rn-222 – mass number decreases by 4; atomic number
decreases by 2
Write an equation for the decay of Am-241
241 Am 4He + YX95 2 Z
241 = 4 + Y
95 = 2 + Z
so Y = 237
so Z = 93
What’s X? X = Np
Radioactive Decay Series• Sometimes 1 transmutation isn’t
enough to achieve stability
• Some radioisotopes go through several changes before they achieve stability (and are no longer radioactive)
β- 14C 14N + 0e
ββ++ 1818F F 1818O + O + 00ee
6 7 -1
8 +1
9
How does the mass number or atomic number change in or decay?
• Go to Table N; find an isotope that decays by α, or , write the equation; see how the mass number (or atomic number) changes
• 226Ra 4 + X so X has to be 222X
• X is Ra-222 – mass number decreases by 4– atomic number decreases by 2
8888 22 8686