Nuclear ChemistryNuclear Chemistry

History of Nuclear ChemistryHistory of Nuclear Chemistry

Henri BecquerelHenri Becquerel – in 1896 he found that uranium – in 1896 he found that uranium ore gave off invisible radiation. This was an ore gave off invisible radiation. This was an accidental discovery using photographic film accidental discovery using photographic film wrapped in light proof paper with a piece of wrapped in light proof paper with a piece of fluorescent uranium salt. The film showed an fluorescent uranium salt. The film showed an image proving that something given off by the image proving that something given off by the salt, rather than light, caused the image. salt, rather than light, caused the image.

Marie CurieMarie Curie and her husband, in 1898, and her husband, in 1898, discovered the new radioactive elements they discovered the new radioactive elements they named polonium and radium.named polonium and radium.

BecquerelBecquerel and the Curies were awarded the 1903 and the Curies were awarded the 1903 Physics Nobel PrizePhysics Nobel Prize

http://www.accessexcellence.org/AE/AEC/CC/historical_background.html

Marie Curie died as a result of complications

due to exposure to radiation

http://nobelprize.org/physics/laureates/1903/becquerel-bio.htmlhttp://nobelprize.org/physics/laureates/1903/becquerel-bio.html

Nuclear ChemistryNuclear Chemistry

Understanding Radioactivity and Understanding Radioactivity and Radioactive DecayRadioactive Decay

Figuring Out Half-LivesFiguring Out Half-LivesTracing the Effects of RadiationTracing the Effects of RadiationThe Basics of Nuclear FissionThe Basics of Nuclear FissionLooking at Nuclear FusionLooking at Nuclear Fusion

It all starts with the AtomIt all starts with the Atom Nuclear Chemistry refers to Nuclear Chemistry refers to

changes that occur in the changes that occur in the dense central core of the dense central core of the atom containing protons (+) atom containing protons (+) and neutrons (0)and neutrons (0)

Atoms of the same element Atoms of the same element with different numbers of with different numbers of neutrons are called neutrons are called isotopesisotopes. Many elements . Many elements have several isotopic formshave several isotopic forms

http://www.lbl.gov/abc/Basic.html

Nuclide – name given to the unstable nucleus of a radioactive atom

How many protons and neutrons are found in an atom of uranium-239?

23992 U

Atomic number = protons There are 92 protons

Mass number = sum of protons and neutrons239 – 92 = 147There are 147 neutrons

Radioactivity and Radioactive DecayRadioactivity and Radioactive Decay

Radioactivity is the spontaneous decay of Radioactivity is the spontaneous decay of an unstable nucleusan unstable nucleus

An unstable nucleus may break apart into An unstable nucleus may break apart into two or more other particles with the two or more other particles with the release of energyrelease of energy

Transmutation is the change which occurs Transmutation is the change which occurs when one element is changed into another when one element is changed into another as a result of an alteration in the nucleus as a result of an alteration in the nucleus (number of protons changes)(number of protons changes)

You can predict particles of radioactive You can predict particles of radioactive decay by balancing nuclear reactionsdecay by balancing nuclear reactions

Reactions are represented as follows:Reactions are represented as follows:Reactants Reactants Products Products

ReactantsReactants are substances you start with are substances you start withProductsProducts are substances being formed are substances being formedThe The reaction arrowreaction arrow indicates that a reaction indicates that a reaction

has taken placehas taken place

http://www.lbl.gov/abc/Basic.html

3535ClCl + + 11nn X? + X? + 11HH1717 0

For a nuclear reaction to be balanced, the sum of all the atomic numbers on the left side of the reaction arrow must equal the sum of all the atomic numbers on the right side of the arrow. The same is true for the mass numbers.

In the above example, an isotope of Chlorine (Cl-35) is bombarded by a neutron. You observe that an isotope of hydrogen (H-1) is created along with another isotope that you need to identify.

1

To figure out the unknown isotope (X) you To figure out the unknown isotope (X) you need to balance the equation. The sum of need to balance the equation. The sum of the atomic numbers on the left is 17 (17 + the atomic numbers on the left is 17 (17 + 0), so you want the sum of atomic 0), so you want the sum of atomic numbers on the right to be 17 also. You numbers on the right to be 17 also. You already have an atomic number of 1 on already have an atomic number of 1 on the right, so the atomic number of the the right, so the atomic number of the unknown is 17-1 = 16.unknown is 17-1 = 16.3535ClCl + + 11nn ??X + X + 11HH

17 0 16 117 0 16 1

3535ClCl + + 11nn X? + X? + 11HH1717 0 116

Now look at the mass numbers in the equation. Now look at the mass numbers in the equation. The sum of the mass numbers on the left is 36 The sum of the mass numbers on the left is 36 (35 + 1), and you want the sum of the mass (35 + 1), and you want the sum of the mass numbers on the right to equal 36, too. Right now numbers on the right to equal 36, too. Right now there is a mass number of 1 on the right; 36 – 1 there is a mass number of 1 on the right; 36 – 1 = 35, so that’s the mass number of the unknown = 35, so that’s the mass number of the unknown isotope. You can now determine that the isotope. You can now determine that the unknown isotope is sulfur (atomic #16), and the unknown isotope is sulfur (atomic #16), and the balanced equation looks like this:balanced equation looks like this:3535ClCl + + 11nn 3535S + S + 11HH

17 0 16 117 0 16 1

3535ClCl + + 11nn ??X + X + 11HH1717 0 116

TransmutationTransmutation

This example represents a This example represents a nuclearnuclear transmutationtransmutation, the conversion of one , the conversion of one element into another. Nuclear element into another. Nuclear transmutation is a process human beings transmutation is a process human beings control. S-35 is an isotope that doesn’t control. S-35 is an isotope that doesn’t exist in nature – it is a manmade isotope. exist in nature – it is a manmade isotope. Alchemy – age old attempt to turn Alchemy – age old attempt to turn

common metals into goldcommon metals into gold

http://www.bayerus.com/msms/fun/pages/periodic/gold/

Natural Radioactive DecayNatural Radioactive Decay Certain isotopes are unstable. Their nucleus Certain isotopes are unstable. Their nucleus

breaks apart, undergoing nuclear decay. breaks apart, undergoing nuclear decay. The nucleus has all the positively charged The nucleus has all the positively charged

protons tightly packed together in an extremely protons tightly packed together in an extremely small space with all the protons repelling each small space with all the protons repelling each other. other.

All elements with 84 or more protons are All elements with 84 or more protons are unstable.unstable.

Other isotopes with fewer than 84 protons can Other isotopes with fewer than 84 protons can be radioactive if the neutron / proton ratio is too be radioactive if the neutron / proton ratio is too high. If the isotope is “neutron rich” it is high. If the isotope is “neutron rich” it is unstable. That’s why some isotopes of an unstable. That’s why some isotopes of an element are stable and others are radioactive.element are stable and others are radioactive.

Naturally occurring radioactive isotopes Naturally occurring radioactive isotopes can decay in the following ways:can decay in the following ways:

Alpha particle emission - Alpha particle emission - ααBeta particle emission - Beta particle emission - ββGamma radiation emission - Gamma radiation emission - γγ

Less common types of radioactive decay:Less common types of radioactive decay:Positron emissionPositron emissionElectron captureElectron capture

Alpha EmissionAlpha EmissionAn alpha particle is the positive nucleus of An alpha particle is the positive nucleus of

a He atom, and is represented as a He atom, and is represented as 44He. It He. It is actually a Heis actually a He2+2+ ion – Helium ion with no ion – Helium ion with no electrons.electrons.

Normally an alpha particle given off picks Normally an alpha particle given off picks up two electrons quickly and becomes a up two electrons quickly and becomes a neutral helium atom. neutral helium atom. (electrons are easy to pick up or lose)(electrons are easy to pick up or lose)

Radon-222 is an example of an isotope Radon-222 is an example of an isotope that undergoes alpha emission as follows:that undergoes alpha emission as follows:222222Rn Rn 218218Po + Po + 44HeHe

2

86 84 2alpha particle

Beta EmissionBeta Emission

Isotopes with high neutron / proton ratio Isotopes with high neutron / proton ratio undergo beta emission.undergo beta emission.

In beta emission, a neutron decays into a In beta emission, a neutron decays into a proton and an electron.proton and an electron.

The atomic number increases by 1, and a The atomic number increases by 1, and a beta particle is given off.beta particle is given off.

Iodine-131 which is used in the detection Iodine-131 which is used in the detection and treatment of thyroid cancer, is a beta and treatment of thyroid cancer, is a beta particle emitter:particle emitter:131131I I 131131Xe + Xe + 00ee

53 54 -1

beta particle

Gamma EmissionGamma Emission Alpha and beta particles have the characteristics Alpha and beta particles have the characteristics

of matter. They have definite masses and of matter. They have definite masses and volumes. volumes.

Because there is no mass change associated Because there is no mass change associated with gamma emission, it is referred to as gamma with gamma emission, it is referred to as gamma radiation emission, and is similar to x-rays (high radiation emission, and is similar to x-rays (high energy, short wavelength electromagnetic energy, short wavelength electromagnetic radiation).radiation).

Gamma radiation emission often accompanies Gamma radiation emission often accompanies both alpha and beta emission, but is not usually both alpha and beta emission, but is not usually shown in a balanced nuclear reaction.shown in a balanced nuclear reaction.

Some isotopes give off large amounts of gamma Some isotopes give off large amounts of gamma radiation such as Cobalt-60, which is used in the radiation such as Cobalt-60, which is used in the radiation treatment of cancer. Gamma rays are radiation treatment of cancer. Gamma rays are focused on the tumor, destroying cells.focused on the tumor, destroying cells.

A problem with gamma radiation:A problem with gamma radiation:

http://www.hulklibrary.com/hulk/home/home.asp

http://www.hulkmovie.com/cast/ericbana.htm

Positron EmissionPositron Emission

Positron emission occurs with some Positron emission occurs with some manmade radioactive isotopes.manmade radioactive isotopes.

A positron is an electron with a positive A positron is an electron with a positive charge.charge.

When a proton decays a neutron and a When a proton decays a neutron and a positron are formed and the positron is positron are formed and the positron is emitted from the nucleus.emitted from the nucleus.

Potassium-40 is an example of a positron Potassium-40 is an example of a positron emitter:emitter:4040K K 4040Ar + Ar + 00ee

19 18 +1

positron

AntimatterAntimatter

Do you watch “Star Trek?”Do you watch “Star Trek?”A positron is a tiny bit of antimatter.A positron is a tiny bit of antimatter.When a positron comes in contact with an When a positron comes in contact with an

electron, both particles are destroyed with electron, both particles are destroyed with the release of energy.the release of energy.

Fortunately, not many positrons are Fortunately, not many positrons are produced, so we don’t have to go around produced, so we don’t have to go around dodging explosions.dodging explosions.

http://kazza.cia.com.au/images/website/startrek-enterpr.jpg

Electron CaptureElectron CaptureElectron capture is a rare type of nuclear Electron capture is a rare type of nuclear

decay in which an electron from the decay in which an electron from the innermost energy level (1s) is captured by innermost energy level (1s) is captured by the nucleus. the nucleus.

This electron combines with a proton This electron combines with a proton becoming a neutron.becoming a neutron.

The following equation shows the electron The following equation shows the electron capture of Polonium-204:capture of Polonium-204:204204Po + Po + 00e e 204204Bi + x-raysBi + x-rays

84 -1 83

With the 1s orbital vacant, electrons drop down releasing energy – x-rays

Half-Lives and Radioactive DatingHalf-Lives and Radioactive Dating

It takes a certain amount of time for half the It takes a certain amount of time for half the atoms in a sample of radioactive material to atoms in a sample of radioactive material to decay. It then takes the same amount of time decay. It then takes the same amount of time for half the remaining radioactive atoms to for half the remaining radioactive atoms to decay, and the same amount of time for half of decay, and the same amount of time for half of those remaining radioactive atoms to decay, and those remaining radioactive atoms to decay, and so on…so on…

The amount of time it takes for one half of a The amount of time it takes for one half of a sample to decay is called the sample to decay is called the half lifehalf life of the of the isotope and is given the symbol: isotope and is given the symbol: t ½t ½

The decay of a radioactive isotope is The decay of a radioactive isotope is exponentialexponential

Radioactive DecayRadioactive Decay

Carbon-14 Radioactive DecayCarbon-14 Radioactive Decay

Half-Lives of some Radioactive IsotopesHalf-Lives of some Radioactive Isotopes

RadioisotopeRadioisotope Radiation EmittedRadiation Emitted Half - LifeHalf - Life

Kr-94Kr-94 BetaBeta 1.4 seconds1.4 seconds

Rn-222Rn-222 AlphaAlpha 3.8 days3.8 days

I-131I-131 BetaBeta 8 days8 days

Co-60Co-60 GammaGamma 5.2 years5.2 years

H-3H-3 BetaBeta 12.3 years12.3 years

C-14C-14 BetaBeta 5,730 years5,730 years

U-235U-235 AlphaAlpha 4.5 billion years4.5 billion years

Re-187Re-187 BetaBeta 70 billion years70 billion years

Radioactive DatingRadioactive Dating Carbon-14 is absorbed by plants from carbon Carbon-14 is absorbed by plants from carbon

dioxide in the atmosphere and enters the food dioxide in the atmosphere and enters the food chain.chain.

As long as an organism is alive, the amount of As long as an organism is alive, the amount of C-14 remains constant.C-14 remains constant.

C-14 begins to decrease at a predictable rate C-14 begins to decrease at a predictable rate when an organism dies. (t ½ of C-14 is 5,730 when an organism dies. (t ½ of C-14 is 5,730 years) years)

Radioactive dating using C-14 has been used to Radioactive dating using C-14 has been used to determine the age of skeletons found at determine the age of skeletons found at archeological sites. archeological sites.

For nonliving substances, scientists use other For nonliving substances, scientists use other isotopes, such as potassium-40.isotopes, such as potassium-40.

Safe HandlingSafe Handling

Knowing about half-lives allows scientists Knowing about half-lives allows scientists to know when a sample of a radioactive to know when a sample of a radioactive material is safe to handle. material is safe to handle.

The rule is that a sample is safe when its The rule is that a sample is safe when its radioactivity has dropped below detection radioactivity has dropped below detection limits. This usually occurs at 10 half lives.limits. This usually occurs at 10 half lives.

If radioactive iodine-131 (t ½ = 8 days) is If radioactive iodine-131 (t ½ = 8 days) is injected into the body to treat thyroid injected into the body to treat thyroid cancer, it will be “gone” in 10 half lives or cancer, it will be “gone” in 10 half lives or 80 days. 80 days.

Measuring RadiationMeasuring Radiation

Curie (Ci) – used to measure radioactivityCurie (Ci) – used to measure radioactivity1 Ci = 3.7 X 101 Ci = 3.7 X 101010 disintegrations per second disintegrations per second

RRadiation adiation AAbsorbed bsorbed DDose (rad) – the ose (rad) – the amount of energy absorbed per gramamount of energy absorbed per gram

RRadiation adiation EEquivalent for quivalent for MMan (rem) – used an (rem) – used to estimate radiation effects on the bodyto estimate radiation effects on the body

Detecting RadiationDetecting Radiation

Geiger CounterGeiger Counter – gas filled metal tube that when – gas filled metal tube that when exposed to radiation causes a current to flow exposed to radiation causes a current to flow creating an audible click from a built in speaker.creating an audible click from a built in speaker.

Scintillation CounterScintillation Counter – uses a specially coated – uses a specially coated phosphorous surface to detect radiation. phosphorous surface to detect radiation. Radiation striking the surface causes bright Radiation striking the surface causes bright flashes of light, or scintillations.flashes of light, or scintillations.

Film badgeFilm badge – worn by people who work near – worn by people who work near radiation sources. It is several layers of radiation sources. It is several layers of photographic film covered with black, light proof photographic film covered with black, light proof paper. Radiation exposure will cause a paper. Radiation exposure will cause a darkening of the film.darkening of the film.

Geiger Geiger countercounter

http://www-istp.gsfc.nasa.gov/Education/wgeiger.html

http://www.orau.org/ptp/collection/dosimeters/keleketmetalfilmbadge.htm

Film Badges

Average Yearly Human Exposure Average Yearly Human Exposure SourceSource Dose (millirems)Dose (millirems)

Cosmic RaysCosmic Rays 2727

Earth & MineralsEarth & Minerals 4747

Building MaterialsBuilding Materials 33

Air (radon)Air (radon) 200200

Body TissuesBody Tissues 2121

Medical TechnologiesMedical Technologies 3030

Nuclear MedicineNuclear Medicine 1414

TV, Industry Waste, JewelryTV, Industry Waste, Jewelry 1010

OtherOther 22

TotalTotal 354354

Maximum recommended dose per year: 500 millirems

Ability of Various Types of Ability of Various Types of Radiation PenetratingRadiation Penetrating

RadiationRadiation Penetration of SkinPenetration of Skin

Alpha particlesAlpha particles 0.05 mm0.05 mm

Beta particlesBeta particles 2.00 mm2.00 mm

Gamma raysGamma rays 50.00 cm50.00 cm

X-raysX-rays 20.00 cm20.00 cm

NeutronsNeutrons VERY LARGEVERY LARGE

Biological Effects of RadiationBiological Effects of Radiation

Dose (rems)Dose (rems) Effect on Human BodyEffect on Human Body

0-250-25 No effectNo effect

25-10025-100 Decrease in white blood cellsDecrease in white blood cells

100-200100-200 Loss of hair, nausea, vomitingLoss of hair, nausea, vomiting

200-500200-500 Severe radiation sicknessSevere radiation sickness

500 and above500 and above Fatal doseFatal dose

Radiation can have two basic effects on the body:

•It can destroy cells with heat

•It can ionize and fragment cells leading to damage, destruction or mutation

http://www.gensuikin.org/english/photo.html

Nuclear FissionNuclear Fission

In the 1930’s scientists discovered that some In the 1930’s scientists discovered that some nuclear reactions can be initiated and controlled. nuclear reactions can be initiated and controlled.

This is usually accomplished by bombarding a This is usually accomplished by bombarding a large isotope with a second, smaller one – large isotope with a second, smaller one – commonly a neutron.commonly a neutron.

The collision causes the larger isotope to break The collision causes the larger isotope to break apart into two or more elements.apart into two or more elements.

This is known as This is known as nuclear fission.nuclear fission. These types of reactions release a lot of energy.These types of reactions release a lot of energy.

Atomic BombsAtomic Bombs The first atomic bomb was The first atomic bomb was

dropped on Hiroshima, dropped on Hiroshima, Japan, on August 6, 1945.Japan, on August 6, 1945.

Two pieces of a fissionable Two pieces of a fissionable isotope are kept apart until isotope are kept apart until it’s time for the bomb to it’s time for the bomb to explode. Conventional explode. Conventional explosives force the two explosives force the two pieces together to cause a pieces together to cause a chain reactionchain reaction releasing a releasing a tremendous amount of tremendous amount of energy instantaneously.energy instantaneously.

http://www.gensuikin.org/english/photo.htmlhttp://www.gensuikin.org/english/photo.html

Fission Chain ReactionFission Chain Reaction

http://www.euronuclear.org/info/encyclopedia/chainreaction.htm

FISSION REACTIONSFISSION REACTIONS

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Energy from Nuclear FissionEnergy from Nuclear Fission

After a fission reaction, the mass of the reactants is less After a fission reaction, the mass of the reactants is less that the original mass of the products. that the original mass of the products.

The loss of matter during the nuclear reaction is called The loss of matter during the nuclear reaction is called the the mass defectmass defect..

The missing matter is converted into energy.The missing matter is converted into energy. The amount of energy produced can be calculated with The amount of energy produced can be calculated with

the following equation:the following equation: E = mcE = mc22

m is the “missing mass”m is the “missing mass” c is the speed of lightc is the speed of light

Nuclear Power Plants – Controlled Energy ReleaseNuclear Power Plants – Controlled Energy Release

A nuclear power plant produces heat through A nuclear power plant produces heat through controlledcontrolled nuclear fission to boil water, which, in nuclear fission to boil water, which, in turn, is used to make steam to turn a turbine turn, is used to make steam to turn a turbine attached to a generator that produces electricity.attached to a generator that produces electricity.

Conventional power plants burn coal, oil or gas, Conventional power plants burn coal, oil or gas, producing air pollution.producing air pollution.

Potential accidents, and radioactive wastes are Potential accidents, and radioactive wastes are problems associated with nuclear power plants.problems associated with nuclear power plants. Large amounts of radioactive isotopes produced Large amounts of radioactive isotopes produced

by nuclear power plants have to be kept safe and by nuclear power plants have to be kept safe and undisturbed for thousands of years.undisturbed for thousands of years.

Nuclear ReactorNuclear Reactor

http://reactor.engr.wisc.edu/power.html

Nuclear Power PlantsNuclear Power Plants

http://www.nrc.gov/info-finder/reactor/

Glen Rose, TX

Approximately 50 miles from Ft. Worth

Nuclear Power Plants - AccidentsNuclear Power Plants - Accidents Three Mile IslandThree Mile Island – In 1979 at the Three Mile Island – In 1979 at the Three Mile Island

Plant in Pennsylvania, a combination of operator error Plant in Pennsylvania, a combination of operator error and equipment failure caused a loss of reactor core and equipment failure caused a loss of reactor core coolant leading to a partial meltdown and the release of coolant leading to a partial meltdown and the release of a small amount of radioactive gas. There was no loss of a small amount of radioactive gas. There was no loss of life or injury to plant personnel or the general population.life or injury to plant personnel or the general population.

Chernobyl, UkraineChernobyl, Ukraine – In 1986, human error and poor – In 1986, human error and poor reactor design contributed to a tremendous overheating reactor design contributed to a tremendous overheating of the reactor core, causing it to rupture. Two explosions of the reactor core, causing it to rupture. Two explosions and a fire resulted, blowing apart the core and scattering and a fire resulted, blowing apart the core and scattering nuclear material into the atmosphere. A small amount of nuclear material into the atmosphere. A small amount of the material traveled to Europe and Asia. Hundreds of the material traveled to Europe and Asia. Hundreds of people died; many others were sick from radiation people died; many others were sick from radiation poisoning and developed cancer. The area is still poisoning and developed cancer. The area is still uninhabitable. The reactor is encased in concrete, and uninhabitable. The reactor is encased in concrete, and must remain undisturbed for hundreds of years. must remain undisturbed for hundreds of years.

ChernobylChernobyl

http://www.answers.com/topic/chernobyl-accident http://www.spaceman.ca/gallery/chernobyl/Chernopik

Nuclear Fusion – Hope for the FutureNuclear Fusion – Hope for the Future

In fusion, lighter nuclei are fused into a In fusion, lighter nuclei are fused into a heavier nucleus, releasing large amounts heavier nucleus, releasing large amounts of energy.of energy.

The fusion process is the reaction that The fusion process is the reaction that powers the sun.powers the sun.

Controlled release of energy from a fusion Controlled release of energy from a fusion reaction could produce an unlimited supply reaction could produce an unlimited supply of energy that has no wastes or of energy that has no wastes or contaminants to harm the atmosphere. contaminants to harm the atmosphere.

Nuclear FusionNuclear Fusion

http://www.lbl.gov/abc/Basic.html

Problems in achieving fusion:Problems in achieving fusion:

Temperature – the fusion process requires an Temperature – the fusion process requires an extremely high activation energy. The heat extremely high activation energy. The heat required would be 40,000,000 K. This is hotter required would be 40,000,000 K. This is hotter than the sun!than the sun!

Time – the nuclei must be held together close Time – the nuclei must be held together close enough and for long enough at an extremely enough and for long enough at an extremely high temperature for the reaction to start – about high temperature for the reaction to start – about 1 second.1 second.

Containment – the best ceramics developed for Containment – the best ceramics developed for the space program would vaporize when the space program would vaporize when exposed to this high temperature.exposed to this high temperature.

Hydrogen BombHydrogen Bomb

In the Hydrogen bomb In the Hydrogen bomb the explosion of a the explosion of a nuclear fission charge nuclear fission charge (atomic bomb) produces (atomic bomb) produces the temperature and the temperature and density so fusion can density so fusion can occur. This fusion results occur. This fusion results in a sudden release of a in a sudden release of a large amount of energy large amount of energy that produces an even that produces an even bigger explosion. bigger explosion.

http://encarta.msn.com/encyclopedia_761557090/Hydrogen_Bomb.html

FUSION REACTIONSFUSION REACTIONS

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Something to RememberSomething to Remember

Radioactive dating is not….Radioactive dating is not….Taking an x-ray technician to the moviesTaking an x-ray technician to the movies