1 NUCLEAR CHEMISTRY 2 Nuclear Chemistry At the conclusion of our time together, you should be able to: 1. List 4 people who contributed to the discovery

1NUCLEAR CHEMISTRYNUCLEAR CHEMISTRY

2Nuclear ChemistryAt the conclusion of our time together,

you should be able to:

1.1. List 4 people who contributed to the discovery of List 4 people who contributed to the discovery of radiation and their contributionradiation and their contribution

2.2. List the subatomic parts of the atom including List the subatomic parts of the atom including quarksquarks

3.3. Explain the difference in isotopes of an atomExplain the difference in isotopes of an atom4.4. Explain alpha, beta, and gamma radiation and Explain alpha, beta, and gamma radiation and

what happens to the nucleuswhat happens to the nucleus5.5. Calculate half-lives of radioactive materialsCalculate half-lives of radioactive materials6.6. List differences between a fusion and fission List differences between a fusion and fission

reactionsreactions

3

Interesting Signs:

4Nuclear ChemistryAt the conclusion of our time together,



5The People Behind the Discovery The People Behind the Discovery

of Radiationof Radiation

6

RoentgenRoentgen (1895) (1895)

•Discovered a mysterious form of radiation was given off even without electron beam. This radiation could pass through paper and other objects but not dense materials (lead, bone).

•Called them X-rays

•Studied fluorescent materials that glowed when hit with a beam of electrons.

7Becquerel (1896)

•Studied fluorescent minerals containing uranium.•Discovered radioactivity by accident on a cloudy day:•Thought that an external source was needed to produce the mysterious radiation.

•Found that uranium emits radiation without external source.

8

All You Really Need To Know You Can Learn From Noah's Ark

7. For safety's sake, travel in pairs.

8. Two heads are better than one.

9

Thought radioactivity was a property of heavy elements.

Pierre and Marie CuriePierre and Marie Curie

During study, discovered new radioactive elements: Polonium and Radium.

Wondered how a small mass can give off a large amount of energy:

Explained by Einstein with Explained by Einstein with E=mcE=mc22..

10

• Difference between the mass of an atom and the mass of its individual particles.

4.00260 amu4.00260 amu 4.03298 amu4.03298 amu

Mass Defect

11

Mass DefectMass Defect

• Some of the mass can be converted into energySome of the mass can be converted into energy• Shown by a very famous equation!Shown by a very famous equation!

E=mcE=mc22

EnergyEnergy

MassMass

Speed of lightSpeed of light

12

Nuclear Binding Energy

• Energy released when a nucleus is formed from nucleons.

• High binding energy = stable nucleus.

E = mcE = mc22

E:E: energy (J)energy (J)m:m: mass defect (kg)mass defect (kg)c:c: speed of lightspeed of light

(3.00×10(3.00×1088 m/s) m/s)

13Nuclear Binding Energy

Unstable nuclides are radioactive and Unstable nuclides are radioactive and undergo radioactive decay.undergo radioactive decay.

14

•Studied radioactivity and named types of nuclear radiation.

RutherfordRutherford

•Discovered that elements decay into other elements after emitting nuclear radiation. Called it Nuclear Decay.•Gold foil experiment revealed that the mass of an atom is concentrated in the nucleus (atom is mostly space)

15

16RadiationSo let’s see if you can:


17Review of the Atom and Review of the Atom and

IsotopesIsotopes

18Review of Atoms and IsotopesAt the conclusion of our time together,



2.2. Explain the difference in isotopes of an atomExplain the difference in isotopes of an atom

19

Euphemisms in Science We all know that some politicians and government spokesmen use certain euphemistic phrases to give an aura of respectability

to descriptions of events or actions which would be offensive when expressed in plain English. The following is a list of

Euphemisms in Science and their translations into plain English.

““It is clear that much additional work will be required It is clear that much additional work will be required before a complete understanding...”before a complete understanding...”

I don't understand this at all!I don't understand this at all!

20The AtomThe Atom

• An atom is the smallest particle of an An atom is the smallest particle of an element that has the chemical properties element that has the chemical properties of the element.of the element.

• The atom is extremely small. One teaspoon of The atom is extremely small. One teaspoon of water has 3 times as many atoms as the Atlantic water has 3 times as many atoms as the Atlantic Ocean has teaspoons of water.Ocean has teaspoons of water.

• If a large sports stadium were an atom, a If a large sports stadium were an atom, a marble on the 50 yard line would represent the marble on the 50 yard line would represent the nucleus.nucleus.

21

An atom consists of a An atom consists of a • nucleus nucleus

– (of protons and neutrons) (of protons and neutrons) • electrons in space about the nucleus.electrons in space about the nucleus.

The AtomThe Atom

NucleusNucleus

Electron CloudElectron Cloud

22

ATOMIC COMPOSITIONATOMIC COMPOSITION

• Protons (pProtons (p++))– + electrical charge+ electrical charge– mass = 1.672623 x 10mass = 1.672623 x 10-24-24 g g– relative mass = 1.007 atomic mass units relative mass = 1.007 atomic mass units

(amu)(amu)

but we can round to 1but we can round to 1

23

ATOMIC COMPOSITIONATOMIC COMPOSITION

• Electrons (eElectrons (e--))– negative electrical chargenegative electrical charge– relative mass = 0.0005 amu relative mass = 0.0005 amu – but we can round to 0but we can round to 0

• Neutrons (nNeutrons (noo))– no electrical chargeno electrical charge– mass = 1.009 amu mass = 1.009 amu – but we can round to 1but we can round to 1

24

ee-1-1 ee-1-1

. . Proton Electron PhotonProton Electron Photon

Mass ComparisonMass Comparison

Proton is aboutProton is about2000 x electron2000 x electron

Electron is aboutElectron is about1,000,000 x photon1,000,000 x photon

25

Familiar Saying

Eschew the implement of correction and vitiate Eschew the implement of correction and vitiate the scion.the scion.

Spare the rod, spoil the child!Spare the rod, spoil the child!

26

Atomic Number, ZAtomic Number, Z

All atoms of the same element have the same All atoms of the same element have the same number of protons in the nucleus, number of protons in the nucleus, ZZ

1313

AlAl

26.98126.981

Atomic NumberAtomic Number

Atomic SymbolAtomic Symbol

Average Atomic MassAverage Atomic Mass

27

Mass Number, AMass Number, A• C atom with 6 protons and 6 neutrons is the C atom with 6 protons and 6 neutrons is the

mass standard mass standard • = 12 atomic mass units (amu)= 12 atomic mass units (amu)

• Mass Number (A)Mass Number (A) = = # protons + # neutrons# protons + # neutrons

• NOT on the periodic tableNOT on the periodic table

• It is the Average atomic mass (which is on the It is the Average atomic mass (which is on the periodic table) rounded to the nearest whole periodic table) rounded to the nearest whole numbernumber

28

In Summary

• Atomic number = the # protons and also Atomic number = the # protons and also the # electronsthe # electrons

• Mass Number = average atomic number Mass Number = average atomic number rounded to the nearest rounded to the nearest whole numberwhole number

• Mass Number = # protons + # neutronsMass Number = # protons + # neutrons

29Remember Isotopes??Remember Isotopes??

11H H 22H H 33HH

30IsotopesIsotopes

Atoms of the same element Atoms of the same element ((same number of protonssame number of protons) with a ) with a differentdifferent number of neutrons number of neutrons..

IsotopesIsotopes

Atoms of the same element Atoms of the same element ((same number of protonssame number of protons) with a ) with a differentdifferent number of neutrons number of neutrons..

11H H 22H H 33HH

31

1212C C 1313CC6 Protons 6 Protons6 Protons 6 Protons

6 Neutrons 7 Neutrons6 Neutrons 7 Neutrons

IsotopesIsotopes

32IsotopesIsotopes

Therefore:The Average Atomic Mass will be some fraction between all

the mass numbers of all the isotopes of that element! For Hydrogen, since most of the isotopes of are in the left

form, the average atomic mass is slightly more than 1 amu.

IsotopesIsotopes

Therefore:The Average Atomic Mass will be some fraction between all

the mass numbers of all the isotopes of that element! For Hydrogen, since most of the isotopes of are in the left

form, the average atomic mass is slightly more than 1 amu.

11H H 22H H 33HH

33

To: Santa Re: Where Are My Gifts?!

Actual E-mails to EmailSanta.com

• I’m sorry for putting all that Ex-lax in your milk last year, but I wasn’t sure if you were real.

• My dad was really mad.

• Bri, 7

34

Tevatron - world's highest-energy particle Tevatron - world's highest-energy particle accelerator.accelerator.Four miles in circumferenceFour miles in circumferenceParticles go around at 99.9999% of the speed Particles go around at 99.9999% of the speed

of light. of light.

Tevatron - world's highest-energy particle Tevatron - world's highest-energy particle accelerator.accelerator.Four miles in circumferenceFour miles in circumferenceParticles go around at 99.9999% of the speed Particles go around at 99.9999% of the speed

of light. of light.

35Particle Particle acceleratoracceleratorParticle Particle acceleratoraccelerator

36

We send protons and antiprotons in We send protons and antiprotons in opposite directions, and smash opposite directions, and smash

them together.them together.

37

38We’ve Discovered Other ParticlesWe’ve Discovered Other ParticlesWe’ve Discovered Other ParticlesWe’ve Discovered Other Particles

Matter Matter anti-Matter anti-Matter

ee+1+1 ee-1-1

Example:Example:

electron electron positron positron

39We’ve Discovered Other ParticlesWe’ve Discovered Other ParticlesWe’ve Discovered Other ParticlesWe’ve Discovered Other Particles

MatterMatter

PP+1+1 PP-1-1

Example:Example:

Proton Proton anti-Proton anti-Proton

anti-Matteranti-Matter

40

Quarks Quarks Leptons Leptons

UpUp electronelectron

DownDown - - 11 33

22 3 3

ee-1-1

We’ve Discovered Other ParticlesWe’ve Discovered Other ParticlesWe’ve Discovered Other ParticlesWe’ve Discovered Other Particles

41

Sub-Subatomic ParticlesSub-Subatomic Particles

• Quarks

• Fast moving points of energy

HeHe Up quark = + 2/3Up quark = + 2/3

Down quark = - 1/3Down quark = - 1/3

• Sum of the charges is the Sum of the charges is the electrical chargeelectrical charge

42

Structure of Sub-Subatomic Particles

Quark Calculations of Charges

Each proton is 2 up quarks and 1 down quark

2(2/3) – 1(1/3) = 4/3 – 1/3 = 3/3 or +1

Each neutron is 2 down quarks and 1 up quark

2(-1/3) + 2/3 = 0

Each electron is composed of 3 down quarks

3(-1/3) = -1

43

A.P. TEST IN ADVANCED BIOLOGY

•

• You have been provided with a razor blade, a piece of gauze, needle and thread and a bottle of scotch. Remove your appendix. Do not suture your work until it has been inspected. You have 15 minutes.

44Review of Atoms and Isotopes Let’s see if you can:


2.2. Explain the difference in isotopes of an atomExplain the difference in isotopes of an atom

45

Self-Check

Isotope Symbol # protons # neutrons

Atomic Mass

Mo-101

H-2

C-14

U-238

Bi-210

He-4

H21

C146

U23892

Bi21083

He42

Mo10142 4242

11

66

9292

8383

22

5959

11

88

146146

127127

22

101101

22

1414

238238

210210

44

46

Proton Neutron ElectronProton Neutron Electron

Mass 1 amu 1 amu 0 amuMass 1 amu 1 amu 0 amu

Charge +1 0 -1Charge +1 0 -1

47

What isWhat is

Made of Made of 3 Quarks3 Quarks

1 up1 up2 down2 down uu

dd

dd

NeutronNeutron

48

What isWhat is

Made of Made of 3 Quarks3 Quarks

2 up2 up1 down1 down

dd

uu

uuProtonProton

49Bill Gates' RulesHere is a list of 11 things that many high

school and college graduates did not learn in school. In his book, Bill Gates talks

about how feel-good, politically-correct teachings created a full generation of kids

with no concept of reality and how this concept has set them up for failure in the

real world.

RULE 4RULE 4

If you think your teacher is tough, wait till you get a If you think your teacher is tough, wait till you get a boss. He doesn't have tenure.boss. He doesn't have tenure.

50Nuclear Reactions and Half-LifeAt the conclusion of our time together,


1.1. Explain alpha, beta, and gamma radiation and Explain alpha, beta, and gamma radiation and what happens to the nucleuswhat happens to the nucleus

2.2. Balance 5 different types of nuclear reactionsBalance 5 different types of nuclear reactions3.3. Calculate half-lives of radioactive materialsCalculate half-lives of radioactive materials

51Nuclear Reactions vs. Normal Nuclear Reactions vs. Normal Chemical ChangesChemical Changes

• Nuclear reactions involve the nucleus• The nucleus opens, and protons and

neutrons are rearranged• The opening of the nucleus releases a

tremendous amount of energy that holds the nucleus together – called what?

• Binding energy• “Normal” Chemical Reactions involve

electrons, not protons and neutrons

52

Types of RadiationTypes of Radiation

e01

He42

• Alpha (Alpha (άά) – a positively charged ) – a positively charged helium isotope - we usually helium isotope - we usually ignore the charge because it ignore the charge because it involves electrons, not protons involves electrons, not protons and neutronsand neutrons

•Beta (Beta (ββ) – an electron) – an electron

•Gamma (Gamma (γγ) – pure energy; called ) – pure energy; called a ray rather than a particlea ray rather than a particle 0

0

53

Other Nuclear ParticlesOther Nuclear Particles

e01

n10• Neutron

• Positron – a positive electron

•Proton – usually referred to as hydrogen-1

•Any other elemental isotope

H11

54

Chemical Compound Quiz

Sodium hydrogen carbonate gives a nice lift to biscuits. Sodium hydrogen carbonate gives a nice lift to biscuits. What is the common name?What is the common name?

Baking PowderBaking Powder

55

Penetrating Ability of Radiation

56

Beta ParticleBeta Particle(Electron)(Electron)

PositronPositronemissionemission

RadioactivityRadioactivity

AlphaAlpha

ParticleParticle

Gamma Particle

Gamma Particle

(light)(light)

57

Gamma Particle (light)Gamma Particle (light)

Beta Particle Beta Particle

(Electron)(Electron)

Alpha ParticleAlpha Particle2 Protons2 Protons2 Neutrons2 Neutrons

Radioactive Particles And RaysRadioactive Particles And Rays

58

Radioactive decayRadioactive decayRadioactivityRadioactivity

Change in the nucleus of an atomChange in the nucleus of an atom

Loss of an Alpha, Beta, or Gamma particleLoss of an Alpha, Beta, or Gamma particle

59

Alpha

emission

Changes

Atomic

Mass

2P 2N

Beta

emission

Neutron

turns into

a Proton

electron

Gamma

emission

light

3 Forms of 3 Forms of Radioactive DecayRadioactive Decay

60

Balancing Nuclear ReactionsBalancing Nuclear Reactions

•In the reactants (starting materials – on the left side of an equation) and products (final products – on the right side of an equation)

Atomic numbers must balanceand

Mass numbers must balance

•Use a particle or isotope to fill in the missing protons and neutrons

6115 Helpful Hints On The Lab

Report from Mr. T’s Vast Lab Experience!!!

Hint #15. When your calculated answers don't Hint #15. When your calculated answers don't match match

the answer you should have gotten the answer you should have gotten utilize the utilize the TFTF22 constant.constant.

TFTF22 constant (Toburen Fudge Factor): constant (Toburen Fudge Factor): that quantity which, when multiplied by, divided by, that quantity which, when multiplied by, divided by, added to or subtracted from the answer you got, gives added to or subtracted from the answer you got, gives you the answer you should have gotten.you the answer you should have gotten.

62Alpha Emission

He Th U 42

23490

23892

parentparentnuclidenuclide

daughterdaughternuclidenuclide

alphaalphaparticleparticle

Numbers must balance!!Numbers must balance!!

occurs when the occurs when the nucleus has too many nucleus has too many protons which cause protons which cause excessive repulsion. excessive repulsion.

63Alpha Emission

U23592Pu239

94 He42

Ex. Plutonium-239 undergoes alpha decayEx. Plutonium-239 undergoes alpha decay

++

232399

Atomic Mass:Atomic Mass: == 232355

44++

9494Atomic #:Atomic #: == 9292 22++

Masses must be equal = Conservation of massMasses must be equal = Conservation of mass

64Beta Emission

e Xe I 0-1

13154

13153

electronelectron

occurs when the neutron to proton ratio occurs when the neutron to proton ratio is too great. is too great.

65

Remember Quark Charges

Beta Emission Means a Neutron becomes a Proton

Each electron is composed of 3 down quarks

3(-1/3) = -1 (Lost)

Each neutron is 2 down quarks and 1 up quark

2(-1/3) + 2/3 = 0 - 3(-1/3) = +1

Neutron becomes a proton

Therefore, mass number stays the same but atomic number goes up one!

66Neutron to ProtonNeutron to Proton

67

XAZPo210

84

Ex. Polonium-210 undergoes beta decay to Ex. Polonium-210 undergoes beta decay to produce this daughter nuclideproduce this daughter nuclide

++

Beta Emission

Atomic Mass:Atomic Mass: 212100

== AA 00++

Atomic #:Atomic #: 8484 == ZZ -1-1++

212100

== AA00-- == 212100

8484 == ZZ11++ == 8585

XAZ == At210

85

e01-

68

e Ar K 01

3818

3819

positronpositron

Positron Emission

Occurs when the neutron to proton ratio is Occurs when the neutron to proton ratio is too small. too small.

69

XAZPo210

84

Ex. Polonium-210 undergoes positron Ex. Polonium-210 undergoes positron emission to produce this daughter nuclideemission to produce this daughter nuclide

++

Positron Emission


== AA 00++

Atomic #:Atomic #: 8484 == ZZ +1+1++

212100

== AA00-- == 212100

8484 == ZZ11-- == 8383

XAZ == Bi210

83

e01

70Electron Capture

Pd e Ag 10646

0-1

10647

electronelectron

occurs when the neutron to proton ratio in the occurs when the neutron to proton ratio in the nucleus is too small. nucleus is too small.

71

XAZPo210

84

Ex. Polonium-210 captures an Ex. Polonium-210 captures an electron to produce this daughter electron to produce this daughter

nuclidenuclide++

Electron Capture


== AA00++

Atomic #:Atomic #: 8484 == ZZ-1-1++

AA == 212100

ZZ == 8383

XAZ == Bi210

83

e01-

72Murphy's Laws

ofScience and Technology

A meeting is an event in which minutes are kept A meeting is an event in which minutes are kept and the hours are lost.and the hours are lost.

73Gamma Emission

Emission of high energy Emission of high energy electromagnetic wave.electromagnetic wave.

occurs when the nucleus is at too high an occurs when the nucleus is at too high an energy. energy.

74

75

XAZPo210

84

Ex. Polonium-210 undergoes gamma Ex. Polonium-210 undergoes gamma decay to produce this daughter nuclidedecay to produce this daughter nuclide

++

Gamma Emission


== AA 00++

Atomic #:Atomic #: 8484 == ZZ 00++

AA == 212100

ZZ == 8484

XAZ ==

00

Po21084

76

Now Lets’ Now Lets’ Consider Consider Nuclear Nuclear

Decay and Decay and Half-Life Half-Life

Band of Band of Stability and Stability and Radioactive Radioactive

DecayDecay

77Nuclear Decay

• Why nuclides decay– need 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

•Transmutation-Transmutation-One One element becomes element becomes another.another.

More than More than 8383 protons protons means that the nuclei is means that the nuclei is unstable (radioactive)unstable (radioactive)

78

Half-life• Half-life (t½)

– Time required for half the atoms of a radioactive nuclide to decay.

– Shorter half-life = less stable.

79

Half-life

nif mm )( 2

1

mmff:: final massfinal mass

mmii:: initial massinitial mass

nn:: # of half-lives# of half-lives

80

Half-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:GIVEN:

tt½½ = 5.0 s = 5.0 s

mmii = 25 g = 25 g

mmff = ? = ?

total time = 60.0 stotal time = 60.0 s

n = 60.0s ÷ 5.0s =12 n = 60.0s ÷ 5.0s =12

WORKWORK::

mmff = m = mii (½) (½)nn

mmff = (25 g)(0.5) = (25 g)(0.5)1212

mmff = 0.0061 g = 0.0061 g

81

Interesting Signs:

82Nuclear Reactions and Half-Life Let’s see if you can:

1.1. Explain alpha, beta, and gamma radiation and Explain alpha, beta, and gamma radiation and what happens to the nucleuswhat happens to the nucleus

2.2. Balance 5 different types of nuclear reactionsBalance 5 different types of nuclear reactions3.3. Calculate half-lives of radioactive materialsCalculate half-lives of radioactive materials

83

Penetrating AbilityPenetrating Ability

84

He42

Types of Radiation?

• Alpha particle ()– helium nucleus paperpaper2+2+

• Beta particle (Beta particle (-)-)– electronelectron

e0-1 1-1-

leadlead

• Positron (Positron (+)+)– positronpositron

e01 1+1+

• Gamma (Gamma ())– high-energy photonhigh-energy photon 00 concreteconcrete

ChargeCharge ShieldingShielding

00

85

XAZPo210

84 He42

Ex. Polonium-210 undergoes alpha decay Ex. Polonium-210 undergoes alpha decay to produce this daughter nuclideto produce this daughter nuclide

++

Alpha Emission


== AA 44++

Atomic #:Atomic #: 8484 == ZZ 22++

212100

== AA44-- == 202066

8484 == ZZ22-- == 8282

XAZ == Pb206

82

86

Remember in Nuclear ReactionsRemember in Nuclear Reactions

• Alpha emissionAlpha emission

Note that mass number (A) goes down by 4 and atomic number (Z) goes down by 2.

Nucleons (nuclear particles… protons and neutrons) are rearranged but conserved

87

Remember in Nuclear ReactionsRemember in Nuclear Reactions

• Beta emissionBeta emission

Note that mass number (A) is unchanged and atomic number (Z) goes up by 1.

88Remember the Other Types of Remember the Other Types of Nuclear ReactionsNuclear Reactions

Positron (Positron (00+1+1): a positive electron): a positive electron

Electron capture: Electron capture: the capture of an electron

207 207

89

The “Y” Generation!!!

90

Learning Check

What radioactive isotope is produced in the following bombardment of boron?

10B + 4He ? + 1n

5 2 0

1313NN77

91

Write Nuclear Equations!

Write the nuclear equation for the beta emitter Co-60.

6060Co - Co - 00e e 6060Ni Ni 27 -1 2827 -1 28

92

Write Nuclear Equations!

In the following reaction, what is being emitted and what is the daughter nuclide?

5959Fe - Fe - 00e e 5858Co Co 26 -1 2726 -1 27

Beta ParticleBeta Particle

93

What is Half-Life?What is Half-Life?

• HALF-LIFEHALF-LIFE is the time that it takes for 1/2 a is the time that it takes for 1/2 a sample to decompose.sample to decompose.

• The rate of a nuclear transformation depends only The rate of a nuclear transformation depends only on the “reactant” concentration.on the “reactant” concentration.

94

Half-LifeHalf-Life

Decay of 20.0 mg of Decay of 20.0 mg of 1515O. What remains after 3 O. What remains after 3 half-lives? After 5 half-lives?half-lives? After 5 half-lives?

95

Kinetics of Radioactive DecayKinetics of Radioactive Decay

For each duration (half-life), one half of the substance

decomposes.

For example: Ra-234 has a half-life of 3.6 days

If you start with 50 grams of Ra-234

After 3.6 days > 25 gramsAfter 3.6 days > 25 grams

After 7.2 days > 12.5 gramsAfter 7.2 days > 12.5 grams

After 10.8 days > 6.25 gramsAfter 10.8 days > 6.25 grams

96

Learning Check!

The half life of I-123 is 13 hr. How much of a 64 mg sample of I-123 is left after 39 hours?

nif mm )( 2

1

X mg = 64 (1/2)X mg = 64 (1/2)33

8.0 mg 8.0 mg

97

Another Interesting Sign:

98Fission vs. Fusion At the conclusion of our time together,


1.1. List differences between a fusion and fission List differences between a fusion and fission reactionreaction

99Nuclear FissionNuclear Fission

100

History:

Hahn & Strassman (1939)Hahn & Strassman (1939)

•Bombarded Uranium-235 samples Bombarded Uranium-235 samples with neutrons expecting the Uranium-with neutrons expecting the Uranium-235 to capture neutrons235 to capture neutrons

•Instead, the products showed Instead, the products showed different chemical properties that different chemical properties that they could not explainthey could not explain

101

•Explained Hahn & Strassman Explained Hahn & Strassman results.results.

•Instead of heavier Uranium, it Instead of heavier Uranium, it had split into smaller elements had split into smaller elements ==

Nuclear FissionNuclear Fission

Meitner & Frisch

102

• Difference between the mass of an atom and the mass of its individual particles.

4.00260 amu4.00260 amu 4.03298 amu4.03298 amu

Remember Mass Defect?Remember Mass Defect?

E = mcE = mc22E:E: energy (J)energy (J)m:m: mass defect mass defect (kg)(kg)c:c: speed of lightspeed of light

(3.00×10(3.00×1088 m/s) m/s)

103

104Nuclear Fission

– – splitting of heavier nuclei splitting of heavier nuclei into lighter nucleiinto lighter nuclei..

U23592 n1

0 Ba13756 Xe84

36 n10

energenergyy

++ ++1515++ ++

105


106


Fission is the splitting of atomsFission is the splitting of atoms

These are usually very large, so that they are not as These are usually very large, so that they are not as

stablestable

Fission chain has two general steps:Fission chain has two general steps:

1.1. Initiation.Initiation. Reaction of a single atom starts the Reaction of a single atom starts the

chain (e.g., chain (e.g., 235235U + neutron)U + neutron)

2.2. PropagationPropagation. . 236236U fission releases neutrons that U fission releases neutrons that

initiate other fissionsinitiate other fissions

107Representation Of A Fission Process.

108

Nuclear Chain Reactions:

•Nuclear Nuclear fission releases fission releases more neutrons more neutrons which trigger which trigger more fission more fission reactionsreactions•The number of The number of ________ ________ released released determines the determines the success of a success of a chain reactionchain reaction

neutronsneutrons

109

Nuclear Fusion

Fusion

small nuclei combine

2H + 3H 4He + 1n +

1 1 2 0

Occurs in the sun and other stars

Energy

110Nuclear Fusion - Energy released when - Energy released when

two light nuclei combine two light nuclei combine or fuseor fuse

•However, a large amount of energy is required to start a fusion reaction:

o Need this energy to overcome ________ forces of protons.o Extremely high temperatures provide start-up energy.

repulsionrepulsion

**More energy is released in fusing hydrogen **More energy is released in fusing hydrogen than in the fission of uranium!!!!than in the fission of uranium!!!!

11H

11H

21H

01e energenerg

yy++ ++ ++

111Nuclear Fusion

112Stars:

energy is produced through fusion

reactions

Fusion occurs until Fe is produced because less energy is released than

required to fuse Fe nuclei.

When this happens the

_____ ____ ____

Star burns outStar burns out

113

Nuclear Fusion

Problems:• Excessive heat can not be contained• Attempts at “cold” fusion have FAILED.• “Hot” fusion is difficult to contain

114

Cold Fusion:

Efforts are being made Efforts are being made to start and to start and sustainsustain a a fusion reaction at lower fusion reaction at lower temperatures, in other temperatures, in other words with a lower words with a lower amount of amount of inputinput energyenergy

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Various Uses of Nuclear Chemistry

Fission over the years has proven to be • Very helpful• Very harmful

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Nuclear Fission & POWERNuclear Fission & POWER

• Currently about 103 Currently about 103

nuclear power plants in nuclear power plants in

the U.S. and about 435 the U.S. and about 435

worldwide.worldwide.

• 17% of the world’s 17% of the world’s

energy comes from energy comes from

nuclear.nuclear.

117Diagram Of A Nuclear Power Plant.

118

119

Radiocarbon DatingRadiocarbon Dating

Radioactive C-14 is formed in the upper atmosphere Radioactive C-14 is formed in the upper atmosphere by nuclear reactions initiated by neutrons in cosmic by nuclear reactions initiated by neutrons in cosmic radiationradiation

1414N + N + 11oon ---> n ---> 1414C + C + 11HH

The C-14 is oxidized to COThe C-14 is oxidized to CO22, which circulates through , which circulates through

the biosphere.the biosphere.

When a plant dies, the C-14 is not replenished.When a plant dies, the C-14 is not replenished.

But the C-14 continues to decay with tBut the C-14 continues to decay with t1/21/2 = 5730 years. = 5730 years.

Activity of a sample can be used to date the sample.Activity of a sample can be used to date the sample.

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Artificial Nuclear ReactionsArtificial Nuclear Reactions

New elements or new isotopes of known elements New elements or new isotopes of known elements are produced by bombarding an atom with a are produced by bombarding an atom with a subatomic particle such as a proton or neutron subatomic particle such as a proton or neutron -- or even a much heavier particle such as -- or even a much heavier particle such as 44He He and and 1111B.B.

Reactions using neutrons are called Reactions using neutrons are called reactions reactions because a because a ray is usually emitted. ray is usually emitted.

Radioisotopes used in medicine are often made by Radioisotopes used in medicine are often made by reactions. reactions.

121

Artificial Nuclear ReactionsArtificial Nuclear Reactions

Example of a Example of a reaction reaction is production of is production of

radioactive radioactive 3131P for use in studies of P uptake in P for use in studies of P uptake in

the body.the body.

31311515P + P + 11

00n n 32321515P + P +

122

Transuranium ElementsTransuranium Elements

Elements beyond 92 Elements beyond 92 (transuranium)(transuranium) made made

starting with an starting with an reaction reaction

2382389292U + U + 11

00n n 2392399292U + U +

2392399292U U 239239

9393Np + Np + 00-1-1

2392399393Np Np 239239

9494Pu + Pu + 00-1-1

123

Nuclear Medicine: ImagingNuclear Medicine: Imaging

Thyroid imaging using Tc-99mThyroid imaging using Tc-99m

124

Food IrradiationFood Irradiation

•Food can be irradiated with Food can be irradiated with rays from rays from 6060Co or Co or 137137Cs.Cs.•Irradiated milk has a shelf life of 3 months Irradiated milk has a shelf life of 3 months

without refrigeration.without refrigeration.•USDA has approved irradiation of meats and USDA has approved irradiation of meats and

eggs.eggs.

125A Negative use of the Fission Process

126A Negative use of the Fission ProcessFat Man

127A Negative use of the Fission ProcessLittle Boy

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Geiger Counter

• Used to detect radioactive substances

129

130

Effects of RadiationEffects of Radiation

131

When I was a kid…

• We didn’t have padding or rubber fragments under our jungle gyms. We had rocks!

• We didn’t have safety belts or air bags in our cars. Most kids had cars that could go 0-60 in less than 6 seconds!! But gas was 30 cents a gallon!!!

• We rode our bikes without helmets.• No sunscreen, just suntan lotion, and got burned to

a crisp.

132

When I was a kid…

• We played with BB guns.• Ran with scissors.• Blew up Barbie dolls with M-80’s.• Wore Halloween costumes with asbestos.

• But for safety….• our moms made us wait an hour after we ate

before we went swimming!!!!

133Fission vs. FusionLet’s see if you can:

1.1. List differences between a fusion and fission List differences between a fusion and fission reactionreaction

134

Fission or Fusion??Fission or Fusion??

135

Familiar Saying

One pyrus malus per diem restrains the arrival of the One pyrus malus per diem restrains the arrival of the Hippocratic apostle.Hippocratic apostle.

An apple a day keeps the doctor away!!An apple a day keeps the doctor away!!

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Documents

1 NUCLEAR CHEMISTRY 2 Nuclear Chemistry At the conclusion of our time together, you should be able to: 1. List 4 people who contributed to the discovery