2 - 1CH 104

Chapter 5: Nuclear Chemistry

RadioactivityNuclear Equations

Radiation DetectionHalf-Life

Medical Applications

2 - 2CH 104

Isotopes of HydrogenIsotopes = Atoms of the same element but

having different masses.

11

21

31

H H H

+

-

+

-

+

-

Protium99.99%

Deuterium0.01%

TritiumTrace %

Average Atomic weight of Hydrogen = 1.00794 amu

2 - 3CH 104

Isotopes of Carbon

Average Atomic weight of C= 12.011 amu

98.89%

C612 C6

13C6

14

1.11% Trace %

++

++

+ +

-

-

-

-

--

-

++

++

+ +

-

-- -

-+

+

++

+ +

-

-

-

--

-

2 - 4CH 104

Radioactive Isotopes

C614

++

++

+ +

-

-

-

--

-+

31

H-

Nucleus is unstableSo falls apart (decays)

Giving radioactive particles

Hydrogen-3Carbon-14

2 - 5CH 104

Radioactive Isotopes in Medicine

Tc43

99m

123 53

I

131 53

I

6027

Co

Diagnose thyroid function

Treat hyperthyroid (destroys cells)

Destroy tumors (g radiation)

Diagnose bone, tissue (most common)

2 - 6CH 104

Alpha Decay

Pb82206 +

+

++

+ +

21084 Po

42

He + +

a Particle

21084 Po Pb82

206 + 42 He

2 - 7CH 104

Beta Decay

N714

146 C

0-1

e -

b Particle+

+

++

+ + ++

++

+ ++

+ -

10

n11

H +0-1

eneutron proton electron

2 - 8CH 104

Beta Decay

N714

146 C

0-1

e -

b Particle+

+

++

+ + ++

++

+ ++

+ -

+0-1e14

6 C N714

2 - 9CH 104

Gamma Decay

99m43 Tc g decay

++

++

+ + ++

++

+ +

9943 Tc

+99m43 Tc Tc43

99 g

2 - 10CH 104

Ionizing Radiation

O HH O HH

-Radiation knocks off an electron

Radiation knocks off an electron

An ionAn ion

C HH

H

H

C HH

H

H

A radicalA radical

Ions & radicals cause damaging chain reactionsIons & radicals cause damaging chain reactions

2 - 11CH 104

Geiger Counter

-

Radiation knocks off an electron

Radiation knocks off an electron

An ionAn ion

Ions detected by Counter

Ions detected by Counter

ArArGas in

instrument tube

Gas in instrument

tube

2 - 12CH 104

Radiation: Penetration through Air

+ +a

-b

g

2 - 4 cm

200 - 300 cm

500 m

2 - 13CH 104

Radiation: Shielding

+ +a

-b

g

Paper Cloth

Heavy Cloth

Pb, thick concrete

2 - 14CH 104

+ +a

-b

g

Tissue Penetration Depth

0.05 mm

4-5 mm

>50 cm

2 - 15CH 104

Nuclear Equations

22688 Ra Rn86

222 + 42 He

: a Radon gas in Buildings

Po84218 + 4

2 He

2 - 16CH 104

13153 I Xe54

131 + 0-1e

: b Thyroid check & treatment

: b Cancer Treatment Nuclear Equations

6027 Co Ni28

60 + 0-1e

2 - 17CH 104

Radiation Detection

1 Ci = 3.7 x 1010disintegrations sec

1 Bq = 1 disintegration sec

# of disintegrations by of 1g Ra

ActivityActivity

Becquerel (Bq)

Curie (Ci):

2 - 18CH 104

Radiation Detection

Absorbed DoseAbsorbed Dose

2 - 19CH 104

+ +a

-b

g

Tissue Penetration Depth0.05 mm

0.06-5 mm

>50 cm

Radiation Absorbed Dose (Rad) (D):

1 rad = 1 x 10-2 J kg tissue

1 rad = 1 x 10-2 J kg tissue

1 rad = 2.4 x 10-3 cal kg tissue

Radiation Detection: Biological Effect

2 - 20CH 104

+ +a

-b

g

Tissue Penetration Depth0.05 mm

0.06-5 mm

>50 cm

Radiation Absorbed Dose (Rad) (D):

1 Gray = 1 J kg tissue

1 Gray = 1 J kg tissue

100 rad = 1 Gray

Radiation Detection: Biological Effect

2 - 21CH 104

Radiation Detection

Biological Damage Biological Damage

2 - 22CH 104

Radiation Equivalent for Man (rem)

a

b

g

1 rem = 1 rad x RBE

RBE20

1

1

RBE20

1

1

Damage (rem) = absorbed dose (rad) X factor

(relative biological effectiveness)

100 rem = 1 sievert (Sv)

2 - 23CH 104

Learning Check

2 - 24CH 104

Learning Check: Solution

2 - 25CH 104

Annual Radiation Exposure in USA

Ground = 15 mrem

Air, H2O, Food = 30 mremCosmic = 40 mrem

Wood,concrete,bricks = 50 mrem

X-rays: Chest = 50 mremDental = 20

Smoking = 35 mrem

TV = 2 mrem

Radon = 200 mrem

Total = 170 mrem / yrTotal = 170 mrem / yr

2 - 26CH 104

Annual Radiation Exposure in USA

2 - 27CH 104

Biological Effects of Radiation

Dose in rem (at one time)0-25 genetic damage possible but usually undetected

25-100 decrease # of white blood cells (temporary)

100-200 mild radiation sickness (vomit, diarrhea, strong decrease # white blood cells)

>300 (diarrhea, hair loss, infection)

500 LD50 for humans

Dose in rem (at one time)0-25 genetic damage possible but usually undetected

25-100 decrease # of white blood cells (temporary)

100-200 mild radiation sickness (vomit, diarrhea, strong decrease # white blood cells)

>300 (diarrhea, hair loss, infection)

500 LD50 for humans

2 - 28CH 104

300 LD50 for dogs

800 LD50 for rats

50,000 LD50 for Bacterium

100,000 LD50 for Insects

Biological Effects of RadiationDose in rem

500 LD50 for humans

2 - 29CH 104

4,500 Lymphoma

5,000 – 6,000 Skin cancer

6,000 Lung cancer

6,000 – 7000 Brain Tumor

Therapeutic Doses of RadiationDose in rem

2 - 30CH 104

FDA approved killing of bacteria with:

0.3 – 1 kGy ionizing radiation from

Co-60 or Cs-137(gamma producers)

2 - 31CH 104

Half-Life

t1/2 = Time for 1/2 sample to decay

13153 I

20 g

t1/2 =

8 days10 g

8 days

5 g

2 - 32CH 104

Half-Life

I-131 8 days

Co-60 5.3 yrs

Tc-99m 6 hrs

I-131 8 days

Co-60 5.3 yrs

Tc-99m 6 hrs

2 - 33CH 104

Half-Life

t1/2 = Time for 1/2 sample to decay

13153 I

20 g

t1/2 =

8 days10 g

8 days

5 g

Youtube: Bill Nye Explains Half Life (1:04)https://www.youtube.com/watch?v=js7weHZIQ5o

2 - 34CH 104

B511

116 C

0+1e +

10

n11

H +0+1

e

proton neutron positron

Positron Emission Tomography (PET)

b+ Positron+

+

+

+ ++0

++

+

+ +0

2 - 35CH 104

g rays image

Shows blood flow

g rays image

Shows blood flowB5

11

116 C

0+1e +

Positron Emission Tomography (PET)

b+ Positron+

+

+

+ ++0

++

+

+ +0

115 B

116 C +

0+1

e

positron

0-1e

electron

2g raysDetectable

-

2 - 36CH 104

g rays image

Shows blood flow

g rays image

Shows blood flowB5

11

116 C

0+1e +

Positron Emission Tomography (PET)

b+ Positron+

+

+

+ ++0

++

+

+ +0

0-1e

electron

2g raysDetectable

-

2g+0+1e

electron gammapositron

0-1e

2 - 41CH 104

Radiometric DatingC-14 dating of artifacts (bones, wood,….); t½ = 5760 years

+0-1e14

6 C N714

Issues:• Production of C-14 by sun varies in atmosphere.• 14CO2(g) amounts vary in atmosphere

U-238 Pb-206 U-235 Pb-207Issues:• Assumes all Pb was once U

K Ar(t ½ K-40 = 1.248 x 109 years)

+4020Ca40

19 K Ar1840

2Issues:• Ar(g) solubility• Starting amount of K-40

2 - 42CH 104

Learning Check

2 - 43CH 104

Learning Check: Solution

2 - 44CH 104

Videos

Video: Frontline NOVA Fukushima: Nuclear Aftershocks (53.41 min)http://video.pbs.org/video/2187854464/

2 - 45CH 104

Learning Check: Chromium-55 undergoes beta decay wth a half life of 3.5 minutes.

What is the primary identity of the sample after decay?

5524 Cr +

2 - 46CH 104

Learning Check: Solution Chromium-55 undergoes beta decay wth a half life of 3.5 minutes.

What is the primary identity of the sample after decay?

5524 Cr Mn25

55 + 0-1e

2 - 47CH 104

Learning Check: Chromium-55 undergoes beta decay wth a half life of 3.5 minutes.

What is the primary identity of the sample after decay?

If you start with 120 g; How much Cr-55 will be left after 14 minutes?

5524 Cr Mn25

55 + 0-1e

2 - 48CH 104

Learning Check: Solution Chromium-55 undergoes beta decay wth a half life of 3.5 minutes.

5524 Cr

120 g

t1/2 =

3.5 min

60 g

3.5 min

What is the primary identity of the sample after decay?

If you start with 120 g; How much Cr-55 will be left after 14 minutes?

5524 Cr Mn25

55 + 0-1e

(7 min Total)

3.5 min

(10.5 min Tot)

3.5 min

(14 min Total)

30 g 15 g 7.5 g