Nuclear Chemistry

Nuclear Chemistry

ImagesImages

http://www.pbs.org/wgbh/nova/physics/sthttp://www.pbs.org/wgbh/nova/physics/stability-elements.htmlability-elements.html

http://http://player.discoveryeducation.com/index.cfmplayer.discoveryeducation.com/index.cfm?guidAssetID?guidAssetID=D2253610-8B06-462A-889D-04A63D6A=D2253610-8B06-462A-889D-04A63D6A9A77&productcode=US9A77&productcode=US

Nuclear DecayNuclear Decay Why nuclides decay…Why nuclides decay…

need stable ratio of neutrons to protonsneed 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

RadiationRadiation

Radiation-it’s the transfer of energyRadiation-it’s the transfer of energy Radioactivity-The spontaneous emission Radioactivity-The spontaneous emission

of radiation by an unstable nucleus.of radiation by an unstable nucleus.

Good vs. BadGood vs. Bad

IonizingIonizing Has enough energy to kick off an ion.Has enough energy to kick off an ion. Very high energyVery high energy

Non ionizingNon ionizing Does not have enough energy to kick off an Does not have enough energy to kick off an

ionion Low energyLow energy

He42

Types of RadiationTypes of Radiation

Alpha particle (Alpha particle ()) helium nucleushelium nucleus paper2+

Beta particle (Beta particle (-)-) electronelectron e0

-1 1-lead

Gamma (Gamma ()) high-energy photonhigh-energy photon

0concrete

Nuclear DecayNuclear Decay

Alpha EmissionAlpha Emission

He Th U 42

23490

23892

parentnuclide

daughternuclide

alphaparticle

Numbers must balance!!

Nuclear DecayNuclear Decay

Beta EmissionBeta Emission

e Xe I 0-1

13154

13153

electron

Nuclear DecayNuclear Decay

Electron CaptureElectron Capture

Pd e Ag 10646

0-1

10647

electron Gamma EmissionGamma Emission

Usually follows other types of decay.Usually follows other types of decay.

Transmutation Transmutation One element becomes another.One element becomes another.

Half-lifeHalf-life

Half-life (tHalf-life (t½½)) Time required for half the atoms of a Time required for half the atoms of a

radioactive nuclide to decay.radioactive nuclide to decay. Shorter half-life = less stable.Shorter half-life = less stable.

Half-lifeHalf-life

nif mm )( 2

1

mf: final massmi: initial massn: # of half-lives

Half-lifeHalf-lifeHalf-lifeHalf-life

n: # of half livest1/2 : half life

2/1ttotaltimen

Half-lifeHalf-lifeHalf-lifeHalf-life

ln

1ln

2

f

i

m

mn

mf: final massmi: initial massn: # of half-lives

Half-lifeHalf-life Fluorine-21 has a half-life of 5.0 seconds. If you Fluorine-21 has a half-life of 5.0 seconds. If you

start with 25 g of fluorine-21, how many grams start with 25 g of fluorine-21, how many grams would remain after 60.0 s?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

Half-lifeHalf-lifeHalf-lifeHalf-life

A sample of a radioactive isotope that was initially A sample of a radioactive isotope that was initially 5000 g decayed for 10,000 years. If 625 g remains 5000 g decayed for 10,000 years. If 625 g remains after this time, what is the half-life of the isotope?after this time, what is the half-life of the isotope?

GIVEN:

t½ = ?

mi = 5000 g

mf = 625 g

total time=10000yrs

n = ?

WORK:n= n =3

n= total time ÷ t1/2

t1/2 = total time/n

t1/2= 10000 ÷ 3

t1/2 = 3333.33 yrs.

ln

1ln

2

f

i

m

mn

Or plug into the equationOr plug into the equation

and solve:and solve:

nif mm )( 2

1

Half-lifeHalf-life Half-lifeHalf-life

GIVEN:

t½ = ?

mi = 5000 g

mf = 625 g

total time=10000yrs

n = ?

WORK:

mf=mi(1/2)n

625g = (5000) (1/2)n

.125=(1/2)n

ln(.125)÷ln(1/2) =nn=3 then plug into n=total time ÷ t1/2

FF issionission

splitting a nucleus into two or more splitting a nucleus into two or more smaller nucleismaller nuclei

1 g of 1 g of 235235U = U = 3 tons of coal3 tons of coal

U23592

FF issionission chain reactionchain reaction - self-propagating reaction - self-propagating reaction critical masscritical mass - -

the minimum the minimum

amount of amount of

fissionablefissionable

material needed material needed

to sustain a to sustain a chain reactionchain reaction

FissionFission

Uranium-235 is the only naturally Uranium-235 is the only naturally occurring element that undergoes fission.occurring element that undergoes fission.

Uranium - 235

FissionFission

Why does fission produce so much energy?Why does fission produce so much energy?

Small quantities of mass are converted into Small quantities of mass are converted into appreciable quantities of energy.appreciable quantities of energy.

E = mc2

FissionFission

1 gram

matter

Energy

700,000

Gallons of high octane

gasoline

http://http://player.discoveryeducation.com/index.cfmplayer.discoveryeducation.com/index.cfm?guidAssetID?guidAssetID=35b0a19c-b72d-4502-92af-6cb6c9078cc=35b0a19c-b72d-4502-92af-6cb6c9078cc9&productcode=US9&productcode=US

FusionFusion combining of two nuclei to form one nucleus of larger masscombining of two nuclei to form one nucleus of larger mass thermonuclear reaction – requires temp of 40,000,000 K to sustainthermonuclear reaction – requires temp of 40,000,000 K to sustain 1 g of fusion fuel = 1 g of fusion fuel =

20 tons of coal20 tons of coal occurs naturally in occurs naturally in

starsstars

HH 31

21

Fission vs. FusionFission vs. Fusion

235235U is limitedU is limited danger of meltdowndanger of meltdown toxic wastetoxic waste thermal pollutionthermal pollution

fuel is abundantfuel is abundant no danger of no danger of

meltdownmeltdown no toxic wasteno toxic waste not yet sustainablenot yet sustainable

FISSION

FUSION

Nuclear PowerNuclear Power

Fission ReactorsFission Reactors Cooling Tower

Nuclear PowerNuclear Power

Fission ReactorsFission Reactors

Nuclear PowerNuclear Power

Fusion ReactorsFusion Reactors (not yet sustainable) (not yet sustainable)

Nuclear PowerNuclear Power

Fusion ReactorsFusion Reactors (not yet sustainable) (not yet sustainable)

Tokamak Fusion Test Reactor

Princeton University

National Spherical Torus Experiment

Synthetic ElementsSynthetic Elements Transuranium ElementsTransuranium Elements

elements with atomic #s above 92elements with atomic #s above 92 synthetically produced in nuclear reactors and acceleratorssynthetically produced in nuclear reactors and accelerators most decay very rapidly most decay very rapidly

Pu He U 24294

42

23892

Radioactive DatingRadioactive Dating

half-life measurements of radioactive half-life measurements of radioactive elements are used to determine the age elements are used to determine the age of an objectof an object

decay rate indicates amount of decay rate indicates amount of radioactive materialradioactive material

EXEX: : 1414C - up to 40,000 yearsC - up to 40,000 years238238U and U and 4040K - over 300,000 yearsK - over 300,000 years

Nuclear MedicineNuclear Medicine

Radioisotope TracersRadioisotope Tracers absorbed by specific organs and used to absorbed by specific organs and used to

diagnose diseasesdiagnose diseases

Radiation TreatmentRadiation Treatment larger doses are used larger doses are used

to kill cancerous cells to kill cancerous cells in targeted organsin targeted organs

internal or external internal or external radiation sourceradiation source

Radiation treatment using-rays from cobalt-60.

Nuclear WeaponsNuclear Weapons

Atomic BombAtomic Bomb chemical explosion is used to form a chemical explosion is used to form a

critical mass of critical mass of 235235U or U or 239239PuPu fission develops into an uncontrolled fission develops into an uncontrolled

chain reactionchain reaction

Hydrogen BombHydrogen Bomb chemical explosion chemical explosion fission fission fusion fusion fusion increases the fission ratefusion increases the fission rate more powerful than the atomic bombmore powerful than the atomic bomb

OthersOthers

Food IrradiationFood Irradiation radiation is used to kill bacteriaradiation is used to kill bacteria

Radioactive TracersRadioactive Tracers explore chemical pathwaysexplore chemical pathways trace water flowtrace water flow study plant growth, photosynthesisstudy plant growth, photosynthesis

Consumer ProductsConsumer Products ionizing smoke detectors - ionizing smoke detectors - 241241AmAm