Chapter 5: Nuclear Chemistry Radioactivity Nuclear Equations Radiation Detection Half-Life Medical Applications

Average Atomic weight of Hydrogen Isotopes of Hydrogen Isotopes = Atoms of the same element but having different masses. 1 2 1 3 1 H H H + - + - + - Protium 99.99% Tritium Trace % Deuterium 0.01% Average Atomic weight of Hydrogen = 1.00794 amu

Average Atomic weight of C= 12.011 amu Isotopes of Carbon C 6 12 C 6 13 C 6 14 - - + - + - + - 98.89% 1.11% Trace % Average Atomic weight of C= 12.011 amu

So falls apart (decays) Giving radioactive particles Radioactive Isotopes 3 1 H C 6 14 - + + - - Hydrogen-3 Carbon-14 Nucleus is unstable So falls apart (decays) Giving radioactive particles

Radioactive Isotopes in Medicine 123 53 I Diagnose thyroid function 131 53 I Treat hyperthyroid (destroys cells) 60 27 Co Destroy tumors (g radiation) Tc 43 99m Diagnose bone, tissue (most common)

Alpha Decay He a Particle Po Pb Po Pb He + 4 2 210 84 + 82 206 210 84

- Beta Decay e C b Particle N n H e -1 14 6 + + - + 7 14 1 1 -1 + -1 e - 14 6 C b Particle + + - + N 7 14 1 n 1 H -1 e + neutron proton electron

- Beta Decay e C b Particle N N e C -1 14 6 + + - + 14 7 14 14 -1 6 7 -1 e - 14 6 C b Particle + + - + N 7 14 14 6 C N 7 14 -1 e +

Gamma Decay 99m 43 Tc g decay + + 99 43 Tc 99m 43 Tc Tc 43 99 g +

Radiation knocks off an electron Ionizing Radiation Radiation knocks off an electron - An ion A radical Ions & radicals cause damaging chain reactions

Radiation knocks off an electron Ions detected by Counter Geiger Counter Radiation knocks off an electron - An ion Gas in instrument tube Ions detected by Counter

- Radiation: Penetration through Air a b g 2 - 4 cm 200 - 300 cm 500 m + 2 - 4 cm b 200 - 300 cm - 500 m g

- Radiation: Shielding a b g Heavy Cloth Pb, thick concrete + Pb, thick concrete Paper Cloth b - g

Tissue Penetration Depth + 0.05 mm 4-5 mm b - >50 cm g

a: Radon gas in Buildings Nuclear Equations a: Radon gas in Buildings 226 88 222 4 2 He Ra Rn + 86 218 4 2 He Po + 84 Cancer

b: Thyroid check & treatment Nuclear Equations b: Cancer Treatment 60 27 Co 60 -1 e Ni + 28 b: Thyroid check & treatment 131 53 I 131 -1 e Xe + 54

Radiation Detection Activity Curie (Ci): # of disintegrations by of 1g Ra Curie (Ci): 1 Ci = 3.7 x 1010disintegrations sec Becquerel (Bq) 1 Bq = 1 disintegration sec

Radiation Detection Absorbed Dose

- Radiation Detection: Biological Effect Tissue Penetration Depth a b + a - b g Tissue Penetration Depth 0.05 mm 0.06-5 mm >50 cm Radiation Absorbed Dose (Rad) (D): 1 rad = 1 x 10-2 J kg tissue 1 rad = 2.4 x 10-3 cal kg tissue

- Radiation Detection: Biological Effect Tissue Penetration Depth a b + 0.05 mm 0.06-5 mm b - >50 cm g Radiation Absorbed Dose (Rad) (D): 1 Gray = 1 J kg tissue 100 rad = 1 Gray

Radiation Detection Biological Damage

Radiation Equivalent for Man (rem) (relative biological effectiveness) a RBE 20 1 b g Damage (rem) = absorbed dose (rad) X factor 1 rem = 1 rad x RBE 100 rem = 1 sievert (Sv)

Learning Check

Learning Check: Solution

Annual Radiation Exposure in USA Total = 170 mrem / yr Cosmic = 40 mrem Air, H2O, Food = 30 mrem X-rays: Chest = 50 mrem Dental = 20 Smoking = 35 mrem TV = 2 mrem Radon = 200 mrem Wood,concrete,bricks = 50 mrem Ground = 15 mrem

Annual Radiation Exposure in USA

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

Biological Effects of Radiation Dose in rem 300 LD50 for dogs 800 LD50 for rats 50,000 LD50 for Bacterium 100,000 LD50 for Insects 500 LD50 for humans

Therapeutic Doses of Radiation Dose in rem 4,500 Lymphoma 5,000 – 6,000 Skin cancer 6,000 Lung cancer 6,000 – 7000 Brain Tumor

FDA approved killing of bacteria with: 0.3 – 1 kGy ionizing radiation from Co-60 or Cs-137 (gamma producers)

Half-Life I t1/2 = Time for 1/2 sample to decay 131 53 5 g 10 g 20 g 8 days 131 53 I 8 days 5 g 10 g 20 g

Half-Life I-131 8 days Co-60 5.3 yrs Tc-99m 6 hrs

Half-Life I t1/2 = Time for 1/2 sample to decay 131 53 5 g 10 g 20 g 8 days 131 53 I 8 days 5 g 10 g 20 g Youtube: Bill Nye Explains Half Life (1:04) https://www.youtube.com/watch?v=js7weHZIQ5o

+ Positron Emission Tomography (PET) C e b+ Positron B H n e 11 6 +1 + +1 e + b+ Positron + + B 5 11 1 H 1 n +1 e + proton neutron positron

- + Positron Emission Tomography (PET) e C e 2g rays b+ Positron -1 e electron 11 6 C +1 e - + 2g rays b+ Positron + Detectable g rays  image Shows blood flow + B 5 11 11 6 11 5 B +1 e C + positron

- + Positron Emission Tomography (PET) e C e 2g rays b+ Positron -1 e electron 11 6 C +1 e - + 2g rays b+ Positron + Detectable g rays  image Shows blood flow + B 5 11 +1 e -1 e 2g + positron electron gamma

Fission Energy Kr U U n Ba Splitting atoms for Energy 91 36 235 92 236 n Energy + unstable 142 56 Ba Uses: Atomic Bomb Nuclear Power

Fission Need critical mass of U-235 to sustain chain rxn to produce enough E for an explosion

Fission U-235 Nuclear Power plants: Controlled fission avoids critical mass

> E than from fission But impractical since heat too high Fusion Combining atoms for Energy + 2 1 H 4 2 He 1 n Deuterium Energy + 100,000,000OC + + Tritium 3 1 H + > E than from fission But impractical since heat too high Uses: Sun Hydrogen Bomb

Radiometric Dating N e C Ar Ca 2 K 14 14 -1 6 7 40 40 40 20 19 18 + + C-14 dating of artifacts (bones, wood,….); t½ = 5760 years 14 6 C N 7 14 -1 e + Issues: Production of C-14 by sun varies in atmosphere. 14CO2(g) amounts vary in atmosphere U-238   Pb-206 U-235   Pb-207 Issues: Assumes all Pb was once U K  Ar (t ½ K-40 = 1.248 x 109 years) 40 19 K Ar 18 40 40 20 Ca 2 + Issues: Ar(g) solubility Starting amount of K-40

Learning Check

Learning Check: Solution

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

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? 55 24 Cr +

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? 55 24 Cr 55 -1 e Mn + 25

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? 55 24 Cr 55 -1 e Mn + 25 If you start with 120 g; How much Cr-55 will be left after 14 minutes?

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? 55 24 Cr 55 -1 e Mn + 25 If you start with 120 g; How much Cr-55 will be left after 14 minutes? 55 24 Cr t1/2 = 3.5 min 3.5 min 3.5 min 3.5 min (7 min Total) (10.5 min Tot) (14 min Total) 15 g 7.5 g 60 g 30 g 120 g