chapter 22 nuclear chemistry i. the nucleus (p. 701 - 704) i. the nucleus (p. 701 - 704) i iv iii ii...

CHAPTERCHAPTER 2222

Nuclear NuclearChemistryChemistry

CHAPTERCHAPTER 2222


I. The NucleusI. The Nucleus(p. 701 - 704)

I. The NucleusI. The Nucleus(p. 701 - 704)

I

IV

III

II

Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Nuclear Binding Nuclear Binding EnergyEnergy

Nuclear Binding Nuclear Binding EnergyEnergy

Unstable nuclides are radioactive and undergo radioactive decay.

U-238

10x108

9x108

8x108

7x108

6x108

5x108

4x108

3x108

2x108

1x108

Fe-56

B-10

Li-6

H-2

He-4

00 20 40 60 80 100 120 140 160 180 200 220 240

Mass number

Bin

ding

ene

rgy

per

nucl

eon

(kJ/

mol

)

CHAPTERCHAPTER 2222

Nuclear Nuclear Chemistry Chemistry

CHAPTERCHAPTER 2222


II. Radioactive II. Radioactive DecayDecay

(p. 705 - 712)

II. Radioactive II. Radioactive DecayDecay

(p. 705 - 712)

I

IV

III

II


He42

Types of RadiationTypes of RadiationTypes of RadiationTypes of Radiation

Alpha particle () helium nucleus paper2+

Beta particle (-) electron e0

-11-

leadPositron (+)

positron e01

1+

Gamma () high-energy photon 0

concrete


Nuclear DecayNuclear DecayNuclear DecayNuclear Decay

Alpha Emission

He Th U 42

23490

23892

parentnuclide

daughternuclide

alphaparticle

Numbers must balance!!



Beta Emission

e Xe I 0-1

13154

13153

electronPositron Emission

e Ar K 01

3818

3819

positronCourtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem


Electron Capture

Pd e Ag 10646

0-1

10647

electron Gamma Emission

Usually follows other types of decay.

Transmutation One element becomes another.


120

100

80

60

40

20

0

Neu

tro

ns

(A-Z

)

0 20 40 60 80 100 120Protons (Z)


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 DECAY SERIES TRANSPARENCYCourtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

P = N

e-captureor

e+ emission

stable nuclei

120

100

80

60

40

20

0N

eutr

on

s (A

-Z)

P = N

0 20 40 60 80 100 120Protons (Z)

stable nuclei

e-captureor

e+ emission

120

100

80

60

40

20

0

Neu

tro

ns

(A-Z

)

P = N

0 20 40 60 80 100 120Protons (Z)

stable nuclei

Why nuclides decay… need stable ratio of neutrons to protons


Half-lifeHalf-lifeHalf-lifeHalf-life

Half-life (t½) Time required for half the atoms of a

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

1/1

1/2

1/4

1/8

1/160R

ati

o o

f R

em

ain

ing

Pota

ssiu

m-4

0 A

tom

sto

Ori

gin

al Pota

ssiu

m-4

0 A

tom

s

0 1 half-life1.3

1 half-lives2.6

3 half-lives3.9

1 half-lives5.2

Time (billions of years)Time (billions of years)

Newly formed rockPotassium

Argon

Calcium

Half-lifeHalf-lifeHalf-lifeHalf-life

nif mm )( 2

1

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


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

start with 25 g of fluorine-21, how many grams 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


CHAPTERCHAPTER 2222


CHAPTERCHAPTER 2222


III. Fission & III. Fission & FusionFusion

(p. 717 - 719)

III. Fission & III. Fission & FusionFusion

(p. 717 - 719)

I

IV

III

II


FF issionissionFF issionission

splitting a nucleus into two or more smaller nuclei

1 g of 235U = 3 tons of coal

U23592


FF issionissionFF issionissionchain reaction - self-propagating reactioncritical mass -

mass required to sustain a chain reaction


FusionFusionFusionFusioncombining of two nuclei to form one nucleus of larger mass thermonuclear reaction – requires temp of 40,000,000 K to sustain1 g of fusion fuel =

20 tons of coaloccurs naturally in

stars

HH 31

21


Fission vs. FusionFission vs. FusionFission vs. FusionFission vs. Fusion

235U is limited danger of meltdown toxic waste thermal pollution

fuel is abundant no danger of meltdown no toxic waste not yet sustainable

FISSION

FUSION


CHAPTERCHAPTER 2222


CHAPTERCHAPTER 2222


IV. ApplicationsIV. Applications(p. 713 - 716)

IV. ApplicationsIV. Applications(p. 713 - 716)

I

IV

III

II


Nuclear PowerNuclear PowerNuclear PowerNuclear Power

Fission Reactors Cooling Tower



Fission Reactors



Fusion Reactors (not yet sustainable)


ITER(International ThermonuclearExperimental Reactor)

TOROIDALFIELD COILS(produces the magnetic fieldwhich confines the plasma)

BLANKET(provides neutron shieldingand converts fusion energyinto hot, high pressure fluid)

FUSIONPLASMACHAMBER(where the fusionreactions occur)

Height 100 feetDiameter 100 feetFusion power 1100 Megawatts


Fusion Reactors (not yet sustainable)

Tokamak Fusion Test Reactor

Princeton University

National Spherical Torus Experiment


Synthetic ElementsSynthetic ElementsSynthetic ElementsSynthetic ElementsTransuranium Elements

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

Pu He U 24294

42

23892


Natural and artificial radioactivity

Natural radioactivityIsotopes that have been here since the earth formed.

Example - Uranium

Produced by cosmic rays from the sun.Example – carbon-14

Man-made RadioisotopesMade in nuclear reactors when we split atoms (fission).

Produced using cyclotrons, linear accelerators,…

Radioactive DatingRadioactive DatingRadioactive DatingRadioactive Dating

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

decay rate indicates amount of radioactive material

EX: 14C - up to 40,000 years238U and 40K - over 300,000

years


Nuclear MedicineNuclear MedicineNuclear MedicineNuclear Medicine

Radioisotope Tracers absorbed by specific organs and

used to diagnose diseases

Radiation Treatment larger doses are used

to kill cancerous cells in targeted organs

internal or external radiation source Radiation treatment

using-rays from cobalt-60.


Nuclear WeaponsNuclear WeaponsNuclear WeaponsNuclear Weapons

Atomic Bomb chemical explosion is used to form a

critical mass of 235U or 239Pu fission develops into an uncontrolled

chain reaction Hydrogen Bomb

chemical explosion fission fusion fusion increases the fission rate more powerful than the atomic bomb


OthersOthersOthersOthers

Food Irradiation radiation is used to kill bacteria

Radioactive Tracers explore chemical pathways trace water flow study plant growth, photosynthesis

Consumer Products ionizing smoke detectors - 241Am


Simplified diagram of fission bomb

Subcriticalmasses

Chemical Explosive

Criticalmass

chapter 22 nuclear chemistry i. the nucleus (p. 701 - 704) i. the nucleus (p. 701 - 704) i iv iii ii...

Documents