Nuclear ChemistryNuclear Chemistry

A A BRIEFBRIEF Overview Overview

Just the BasicsJust the Basics

Nuclear chemistry is not a huge focus, but Nuclear chemistry is not a huge focus, but you should be aware of the basicsyou should be aware of the basics

There will be no problem set There will be no problem set BUT…you should review Chapter 23BUT…you should review Chapter 23

The sections on applications of nuclear The sections on applications of nuclear chemistry make for very interesting readingchemistry make for very interesting reading

What Is Radioactivity?What Is Radioactivity?

RadioactivityRadioactivity - - The process by which The process by which atoms spontaneously emit high energy atoms spontaneously emit high energy particles or rays from their nucleus.particles or rays from their nucleus.

First observed by Henri Becquerel in 1896.First observed by Henri Becquerel in 1896.

Radioactive elementsRadioactive elementsHe

Rn

XeI

KrBrSe

ArClS

NeFO

P

NC

H

Li

Na

Cs

Rb

K

TlHgAuHfLuBa

Fr

PtIrOsReWTa PoBiPb

Be

Mg

Sr

Ca

CdAgZrY PdRhRuTcMoNb

LrRa

ZnCuTiSc NiCoFeMnCrV

In SbSn

Ga Ge

Al

At

Te

As

Si

B

Gd TbSm EuNd

U

PmCe

Th

Pr

Pa

YbLa Er TmDy Ho

Cm BkPu AmNp NoAc Fm MdCf Es

Rf Db Sg Bh Hs Mt 110 111 112

Types of RadiationTypes of Radiation Alpha (Alpha ())

Nucleus of Helium-4Nucleus of Helium-4 2+ charge2+ charge Symbol: Symbol: oror

Beta (Beta ()) Composed of electronsComposed of electrons 1- charge1- charge Symbol: Symbol: oror

Gamma (Gamma ()) Electromagnetic radiationElectromagnetic radiation No charge or massNo charge or mass

Unaffected by EM fieldsUnaffected by EM fields Highest energy form of radiationHighest energy form of radiation

242He 42

e01 01

Types of Radioactive DecayTypes of Radioactive Decay Alpha decayAlpha decay

Alpha particle is releasedAlpha particle is released ExampleExample

Beta decayBeta decay Three types:Three types:

Electron emission (neutron decays into an electron & a proton; antineutrino also released)Electron emission (neutron decays into an electron & a proton; antineutrino also released) ExampleExample

Positron emission (positron & neutrino are released)Positron emission (positron & neutrino are released) ExampleExample

Electron capture (an electron is captured by the nucleus)Electron capture (an electron is captured by the nucleus) ExampleExample

Gamma decayGamma decay Results from the emission of a photon of EM radiationResults from the emission of a photon of EM radiation Nucleus of nuclide goes from an excited state to a ground stateNucleus of nuclide goes from an excited state to a ground state

RnRa 22286

42

22688

NpU 23993

01

23992

BiPo 20783

01

20784

LieBe 73

01

74

ExampleExample A patient is given radioactive iodine to test thyroid A patient is given radioactive iodine to test thyroid

function. What happens to the iodine?function. What happens to the iodine?

Is this equation balanced?Is this equation balanced?

You must see if the mass and charge are the same on You must see if the mass and charge are the same on both sides.both sides.

131 53 I Xe + - + 131

54

ExampleExample

131 53I Xe + + 131

54

Mass 53 protons 54 protons 78 neutrons 77 neutrons 131 total mass 131 total mass

Charge+53, protons +54 charge, protons

-1 charge from -

+53 total charge +53 total charge

Yes - it’s balanced

e0-1

Why atoms decayWhy atoms decay Some nuclear arrangements are less Some nuclear arrangements are less

stable than others.stable than others.

A radioactive isotope decays to form a A radioactive isotope decays to form a more stable nucleus.more stable nucleus.

It decays by emitting:It decays by emitting: - mass- mass (alpha particles)(alpha particles) - charge- charge (beta particles)(beta particles) - energy- energy (gamma rays)(gamma rays)

There are other ways but these are not There are other ways but these are not seen in nature.seen in nature.

Half-life examplesHalf-life examples

Name Half-life Name Half-life

Carbon-14Carbon-14 5730 years 5730 years Sodium-24Sodium-24 15 hours 15 hours Iron-59Iron-59 45 days 45 days Cobalt-60Cobalt-60 5.3 years 5.3 years Nickel-63Nickel-63 100 years 100 years Uranium-235Uranium-235 704 million years 704 million years

Nuclear powerNuclear power

Power can be obtained two ways.Power can be obtained two ways.

FissionFission Splitting atomsSplitting atoms• Get energy if the nucleus is big.Get energy if the nucleus is big.• The smaller ones are more stable.The smaller ones are more stable.• What we do in nuclear reactors.What we do in nuclear reactors.

FusionFusion Joining atomsJoining atoms• Get energy if the nuclei are small.Get energy if the nuclei are small.• The larger one is more stable.The larger one is more stable.• This is how the sun works.This is how the sun works.

Nuclear FissionNuclear Fission

Chain reactionChain reaction

Shielding and Shielding and types of radiationtypes of radiation

Alpha particlesAlpha particlesBlocked by 1 cm of air.Blocked by 1 cm of air.

Beta particlesBeta particlesRequires 1 mm of aluminum to block.Requires 1 mm of aluminum to block.

Gamma raysGamma raysMost penetrating. Need concrete or lead Most penetrating. Need concrete or lead

to provide adequate protection.to provide adequate protection.

X-raysX-raysThe same as gamma rays.The same as gamma rays.

Uses of radionuclidesUses of radionuclidesOur ability to measure radioactivity is very Our ability to measure radioactivity is very

sensitive. As a result, radioisotopes have sensitive. As a result, radioisotopes have a number of uses.a number of uses.

In addition, its interaction with living In addition, its interaction with living matter can also be exploited.matter can also be exploited.

Uses includesUses includes• Dating techniquesDating techniques• Cancer treatmentCancer treatment• TracersTracers• ImagingImaging• Testing methodsTesting methods

Carbon datingCarbon dating

Carbon-14 is constantly being produced in the upper Carbon-14 is constantly being produced in the upper atmosphere by cosmic rays at an almost constant atmosphere by cosmic rays at an almost constant rate.rate.

N + N + nn C + C + HH

It rapidly combines with oxygen in the air to make It rapidly combines with oxygen in the air to make COCO22..

1414C + OC + O221414COCO22

147

10

146

11

Carbon datingCarbon dating

• After death, the carbon-14 decays with a half-life of 5730 After death, the carbon-14 decays with a half-life of 5730 years.years.

• We can tell how old things are based on the amount of We can tell how old things are based on the amount of carbon-14 that remains.carbon-14 that remains.

• The method is pretty good in the 1,000-20,000 year range.The method is pretty good in the 1,000-20,000 year range.

• Ideal tool for dating the artifacts of man - or at least it was. Ideal tool for dating the artifacts of man - or at least it was. Materials like plastics are Materials like plastics are 1414C depleted. C depleted.

Medical applicationsMedical applications

Cancer therapyCancer therapy

• Radiation both causes and can treat cancerRadiation both causes and can treat cancer

• Radiation causes molecules in the cell to Radiation causes molecules in the cell to break apart - ionizationbreak apart - ionization

• Most significant damage is when DNA is Most significant damage is when DNA is destroyed.destroyed.

• Effect is greatest in rapidly growing cells.Effect is greatest in rapidly growing cells.

Examples of Examples of radiation treatmentradiation treatment

External bombardmentExternal bombardment 6060CoCo - expose area to gamma rays.- expose area to gamma rays. ImplantsImplants

182182TaTa - used as wire, treatment of eye.- used as wire, treatment of eye.

137137CsCs - use in a balloon catheter for - use in a balloon catheter for bladder. bladder.

Interstitial therapyInterstitial therapy198198AuAu - inject directly into tumor.- inject directly into tumor.

Internal irradiationInternal irradiation131131II - Ingest solution, goes to thyroid.- Ingest solution, goes to thyroid.

Nuclear tracersNuclear tracers

Our ability to measure radiation is VERY Our ability to measure radiation is VERY sensitive.sensitive.

Can introduce a small amount of a radioactive Can introduce a small amount of a radioactive material and see where it goes in the body or material and see where it goes in the body or even within a cell culture - Tracerseven within a cell culture - Tracers

Can be used to measure small amounts of Can be used to measure small amounts of chemicals in the body like hormones - chemicals in the body like hormones - RadioimmunoassayRadioimmunoassay