Nuclear Chemistry. Nuclear Symbols Element symbol Mass number, A (p + + n o ) Atomic number, Z...
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Transcript of Nuclear Chemistry. Nuclear Symbols Element symbol Mass number, A (p + + n o ) Atomic number, Z...
Nuclear ChemistryNuclear Chemistry
Nuclear SymbolsNuclear Symbols
23592U
Element symbol
Mass number, A (p+ + no)
Atomic number, Z(number of p+)
Balancing Nuclear EquationsBalancing Nuclear Equations
nKrBanU 10
9136
14256
10
23592 3
Areactants = Aproducts
Zreactants = Zproducts
235 + 1 = 142 + 91 + 3(1)
92 + 0 = 56 + 36 + 3(0)
Balancing Nuclear Equations Balancing Nuclear Equations #2#2
42
22688Ra
226 = 4 + ____222
222
88 = 2 + ___86
86
Atomic number 86 is radon, Rn
Rn
Balancing Nuclear Equations Balancing Nuclear Equations #3#3
nInU 10
13953
10
23592 2
235 + 1 = 139 + 2(1) + ____95
3992 + 0 = 53 + 2(0) + ____
3995
Atomic number 39 is yttrium, Y
Y
Alpha DecayAlpha Decay
Alpha production (Alpha production (): ):
an alpha particle is aan alpha particle is a
helium nucleushelium nucleus
ThHeU 23490
42
23892
Alpha decay is limited to heavy, radioactive
nuclei
ThU 23490
42
23892
242
242 orHe
Alpha Alpha RadiationRadiation
Limited to VERY large nucleii.
Beta DecayBeta Decay
Beta production (Beta production ():):A beta particle is an A beta particle is an electron ejected from electron ejected from the nucleusthe nucleus
ePaTh 01
23491
23490
Beta emission converts a neutron to a proton
0123491
23490 PaTh
0101 ore
Beta Beta RadiatioRadiatio
nn
Converts a neutron into a proton.
Gamma Ray ProductionGamma Ray Production
Gamma ray production (Gamma ray production ():):
92238
24
90234
002U He Th
Gamma rays are high energy photons produced in association with other forms of decay.
Gamma rays are massless and do not, by themselves, change the nucleus
Deflection of Decay ParticlesDeflection of Decay Particles
Opposite charges_________ each other.
Like charges_________ each other.
attract
repel
Positron ProductionPositron Production
Positron emission:Positron emission:Positrons are the anti-particle of the electron
1122
10
1022Na e Ne
Positron emission converts a proton to a neutron
e01
Electron CaptureElectron Capture
Electron capture: (inner-orbital Electron capture: (inner-orbital electron is captured by the nucleus)electron is captured by the nucleus)
80201
10
79201
00Hg e Au
Electron capture converts a proton to a neutron
Types of RadiationTypes of Radiation
NuclearNuclearStabilityStability
Decay will occur in such a way as to return a nucleus to the band (line) of stability.The most stable nuclide is Iron-56
If Z > 83, the nuclide is radioactive
A A Decay Decay SeriesSeries
A radioactive nucleus reaches a stable A radioactive nucleus reaches a stable state by a series of stepsstate by a series of steps
Half-life ConceptHalf-life Concept
Decay KineticsDecay Kinetics
Decay occurs by first order kinetics (the rate of decay is proportional to the number of nuclides present)
ktN
N
0
lnN = number of nuclides remaining at time t
N0 = number of nuclides present initially
k = rate constant
t = elapsed time
Calculating Half-lifeCalculating Half-life
kkt
693.0)2ln(2/1
t1/2 = Half-life (units dependent on rate constant, k)
Sample Half-LivesSample Half-Lives
Nuclear Fission and FusionNuclear Fission and Fusion
FusionFusion:: Combining two light nuclei to Combining two light nuclei to form a heavier, more stable nucleus.form a heavier, more stable nucleus.
01
92235
56142
3691
013n U Ba Kr n
23
11
24
10He H He e
FissionFission: : Splitting a heavy nucleus into Splitting a heavy nucleus into two nuclei with smaller mass numbers.two nuclei with smaller mass numbers.
Energy and MassEnergy and MassNuclear changes occur with small but Nuclear changes occur with small but measurable losses of mass. The lost mass is measurable losses of mass. The lost mass is called the mass defect, and is converted to called the mass defect, and is converted to energy according to Einstein’s equation:energy according to Einstein’s equation:
E = E = mcmc22
mm = mass defect = mass defectEE = change in energy = change in energy
cc = speed of light = speed of light
Because c2 is so large, even small amounts of mass are converted to enormous amount of energy.
FissionFission
Fission ProcessesFission Processes
Event
NeutronsCausingFission Result
subcritical < 1 reaction stopscritical = 1 sustained reactionsupercritical > 1 violent explosion
A self-sustaining fission process is A self-sustaining fission process is called a chain reaction.called a chain reaction.
A Fission ReactorA Fission Reactor
FusioFusionn