Nuclear Reactions. Balancing Nuclear Equations Conservation of: Conservation of: Atomic Number (subscript) Atomic Mass (superscript)
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Nuclear Reactions
BalancingBalancing Nuclear Nuclear EquationsEquations
Conservation of:Conservation of:
Atomic NumberAtomic Number (subscript) (subscript)
Atomic MassAtomic Mass (superscript) (superscript)
Balancing Nuclear EquationsBalancing Nuclear Equations
1616N N 00e + e + 1616OO7 -1 8
Conservation of mass number: 16 = 0 + 16
Conservation of atomic number: 7 = -1 + 8
Natural TransmutationNatural Transmutation
1 term on reactant side1 term on reactant side Original isotopeOriginal isotope
2 terms on product side2 terms on product side Emitted Particle Emitted Particle New IsotopeNew Isotope
Happens all by itselfHappens all by itself -- Not affected Not affected by by anythinganything in environment in environment
Natural TransmutationNatural Transmutation
1616N N 00e + e + 1616OO7 -1 8
1 term reactant side
2 terms product side
Artificial TransmutationArtificial Transmutation Man: Man: causes it to happencauses it to happen by by
smashing particles into one smashing particles into one anotheranother
2 terms on reactant side2 terms on reactant side Original IsotopeOriginal Isotope Particle that hit it: neutron, Particle that hit it: neutron, proton, or proton, or -particle-particle
Product side usually 2 termsProduct side usually 2 terms
Artificial TransmutationArtificial Transmutation
2727Al + Al + 44He He 3030P + P + 11nn1
3
2 15 0
Original isotope (target nucleus)
“Bullet”
Bombarding with Protons, Bombarding with Protons, protons and protons and -particles -particles - do damage - do damage
when hit target nucleuswhen hit target nucleus
(+) charge & large mass: must be (+) charge & large mass: must be accelerated to high speeds to accelerated to high speeds to overcome repulsive forcesovercome repulsive forces•magnetic and electric fields used to magnetic and electric fields used to
accelerate accelerate
What is an accelerator?What is an accelerator?
accelerator is vacuum chamber (long accelerator is vacuum chamber (long pipe) surrounded by vacuum pumps, pipe) surrounded by vacuum pumps, magnets, high voltage instruments & magnets, high voltage instruments & electronic circuitselectronic circuits
inside pipe, particles are accelerated inside pipe, particles are accelerated to very high speeds & smashed into to very high speeds & smashed into each othereach other
FermiLab
ring circumference = 4mi !(≈ 21km)
Neutron CaptureNeutron Capture
Neutrons:Neutrons:•neutral - aren't repelled by (+) neutral - aren't repelled by (+)
nucleusnucleus•no need to be accelerated no need to be accelerated
good thing since can’t accelerate good thing since can’t accelerate them!them!
Artificial TransmutationArtificial Transmutation
2727Al + Al + 44He He 3030P + P + 11nn1313 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 have 2 reactants!
FissionFission ReactionReaction
InvolvesInvolves splitting heavy splitting heavy nucleus into 2 lighter nucleinucleus into 2 lighter nuclei
FissionFission FFiissssiion = Don = Diivviissiionon
heavy nucleus: FM heavy nucleus: FM > > 100 amu100 amu
reactant side 2 terms:reactant side 2 terms: 1 heavy isotope (U-235, Pu-239)1 heavy isotope (U-235, Pu-239) Bombarding particle – usually neutronBombarding particle – usually neutron
product side at least 2 terms:product side at least 2 terms: 2 medium-weight isotopes2 medium-weight isotopes 11++ neutrons neutrons Huge amount energy releasedHuge amount energy released
FissionFission235235U + U + 11n n 9191Kr + Kr + 142142Ba + 3Ba + 311n + energyn + energy
9292 00 3636 5656 00
235235U + U + 11n n 7272Zn + Zn + 160160Sm + 4 Sm + 4 11n + energyn + energy9292 00 3030 006262
>>200 different product isotopes have 200 different product isotopes have been identifiedbeen identified
small amount mass is converted to small amount mass is converted to energy by E = mcenergy by E = mc22
Fission Chain ReactionFission Chain Reaction
Fission Chain ReactionFission Chain Reaction
Controlled – nuclear reactorControlled – nuclear reactor
Uncontrolled – bombUncontrolled – bomb
FFuusionsion nnuuclei clei uunitenite
reactant side 2 small nucleireactant side 2 small nuclei • H + H; H + He; He + He … (no larger than Li)H + H; H + He; He + He … (no larger than Li)
Product side: Product side: • 1 nucleus (still pretty small) &1 nucleus (still pretty small) &• maybe a particlemaybe a particle
Source of sSource of suun’s energyn’s energy
22H + H + 33H H 44He + He + 11n + energyn + energy11 11 22 00
CERN particles travel just below speed of light;
particles make 400 million revs of ring in 10 hrs
27 km ring
SLAC LBL
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