Transcript
Page 1: CHAPTER 22  Nuclear  Chemistry

CHAPTER 22

Nuclear

Chemistry

CHAPTER 22

Nuclear

ChemistryII. Radioactive II. Radioactive

DecayDecay(p. 705 - 712)

II. Radioactive II. Radioactive DecayDecay

(p. 705 - 712)

I

IV

III

II

Page 2: CHAPTER 22  Nuclear  Chemistry

He42

A. Types of RadiationA. Types of RadiationA. Types of RadiationA. Types of Radiation

Alpha particle () helium nucleus paper2+

Beta particle (-) electron e0

-11-

leadPositron (+)

positron e01+

1+

Gamma () high-energy photon 0

concrete

Page 3: CHAPTER 22  Nuclear  Chemistry

B. Nuclear DecayB. Nuclear DecayB. Nuclear DecayB. Nuclear Decay

Alpha Emission

He Th U 42

23490

23892 +→

parentnuclide

daughternuclide

alphaparticle

Numbers must balance!!

Page 4: CHAPTER 22  Nuclear  Chemistry

B. Nuclear DecayB. Nuclear DecayB. Nuclear DecayB. Nuclear Decay

Beta Emission

e Xe I 0-1

13154

13153 +→

electronPositron Emission

e Ar K 01

3818

3819 ++→

positron

Page 5: CHAPTER 22  Nuclear  Chemistry

B. Nuclear DecayB. Nuclear DecayB. Nuclear DecayB. Nuclear Decay

Electron Capture

Pd e Ag 10646

0-1

10647 →+

electronGamma Emission

Usually follows other types of decay.

Transmutation One element becomes another.

Page 6: CHAPTER 22  Nuclear  Chemistry

B. Nuclear DecayB. Nuclear DecayB. Nuclear DecayB. Nuclear 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 →+

DECAY SERIES TRANSPARENCY

Page 7: CHAPTER 22  Nuclear  Chemistry

C. Half-lifeC. Half-lifeC. Half-lifeC. Half-life

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

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

Page 8: CHAPTER 22  Nuclear  Chemistry

C. Half-lifeC. Half-lifeC. Half-lifeC. Half-life

nif mm )( 2

1=

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

Page 9: CHAPTER 22  Nuclear  Chemistry

C. Half-lifeC. Half-lifeC. Half-lifeC. 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 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


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