chapter 22 nuclear chemistry

CHAPTER 22 Nuclear

Chemistry

I. The Nucleus(p. 701 - 704)

I

IV

III

II

B. Nuclear Binding Energy

Energy released when a nucleus is formed from nucleons.

High binding energy = stable nucleus.

E = mc2E: energy (J)m: mass defect (kg)c: speed of light

(3.00×108 m/s)

CHAPTER 22 Nuclear

Chemistry

II. Radioactive Decay

(p. 705 - 712)

I

IV

III

II

He42

A. Types of RadiationAlpha particle ()

helium nucleus

paper2+

Beta particle (-) electron e0

-11- lead

Positron (+) positron e0

11+

Gamma () high-energy photon 0

concrete

B. Nuclear DecayAlpha Emission

He Th U 42

23490

23892

parentnuclide

daughternuclide

alphaparticle

Numbers must balance!!

B. Nuclear DecayBeta Emission

e Xe I 0-1

13154

13153

electronPositron Emission

e Ar K 01

3818

3819

positron

B. Nuclear DecayElectron Capture

Pd e Ag 10646

0-1

10647

electronGamma Emission

Usually follows other types of decay.Transmutation

One element becomes another.

B. Nuclear DecayWhy 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 TRANSPARENCY

C. Half-lifeHalf-life (t½)

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

Shorter half-life = less stable.

C. Half-life

nif mm )( 2

1

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

C. Half-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 smi = 25 gmf = ?total time = 60.0 sn = 60.0s ÷ 5.0s =12

WORK:mf = mi (½)n

mf = (25 g)(0.5)12

mf = 0.0061 g

CHAPTER 22 Nuclear

Chemistry

III. Fission & Fusion

(p. 717 - 719)

I

IV

III

II

A. F issionsplitting a nucleus into two or more smaller

nuclei1 g of 235U =

3 tons of coal

U23592

A. F issionchain reaction - self-propagating reactioncritical mass -

mass required to sustain a chain reaction

B. Fusioncombining 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

C. Fission vs. Fusion

235U is limiteddanger of

meltdown toxic waste thermal pollution

fuel is abundantno danger of

meltdownno toxic wastenot yet sustainable

FISSION

FUSION

CHAPTER 22 Nuclear

Chemistry

IV. Applications(p. 713 - 716)

I

IV

III

II

A. Nuclear PowerFission Reactors Cooling Tower

A. Nuclear PowerFission Reactors

A. Nuclear PowerFusion Reactors (not yet sustainable)

A. Nuclear PowerFusion Reactors (not yet sustainable)

Tokamak Fusion Test Reactor

Princeton University

National Spherical Torus Experiment

B. Synthetic 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

C. Radioactive Datinghalf-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

D. Nuclear MedicineRadioisotope 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.

E. Nuclear WeaponsAtomic 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

F. OthersFood Irradiation

radiation is used to kill bacteriaRadioactive Tracers

explore chemical pathways trace water flow study plant growth, photosynthesis

Consumer Products ionizing smoke detectors - 241Am