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