1 Nuclear Chemistry

2 Radioactivity One of the pieces of evidence for the fact that atoms are made of smaller particles came from the work of ________ ( ).One of the pieces of evidence for the fact that atoms are made of smaller particles came from the work of ________ ( ). She discovered ________, the spontaneous disintegration of some elements into smaller pieces.She discovered ________, the spontaneous disintegration of some elements into smaller pieces.

3 Some nuclei are unstable Unstable nuclei will naturally release particles and/or energy to become more stable

4 Nuclear Radioactivity Emission of matter and/or energy from the nucleus of an atom

5 Marie Sklodowska and Pierre Curie

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7 Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleusNuclear reactions involve the nucleus The nucleus opens, and protons and neutrons are rearrangedThe nucleus opens, and protons and neutrons are rearranged The opening of the nucleus releases a tremendous amount of energy that holds the nucleus together – called binding energyThe opening of the nucleus releases a tremendous amount of energy that holds the nucleus together – called binding energy “Normal” Chemical Reactions involve electrons, not protons and neutrons“Normal” Chemical Reactions involve electrons, not protons and neutrons

8 Henri Becquerel

9 Penetrating Ability

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11 Mass Defect Some of the mass can be converted into energySome of the mass can be converted into energy Shown by a very famous equation!Shown by a very famous equation! E=mc 2 EnergyMass Speed of light

12 Types of Radiation Alpha (ά) – a positively charged helium isotope - we usually ignore the charge because it involves electrons, not protons and neutrons Alpha (ά) – a positively charged helium isotope - we usually ignore the charge because it involves electrons, not protons and neutrons Beta (β) – an electronBeta (β) – an electron Gamma (γ) – pure energy; called a ray rather than a particleGamma (γ) – pure energy; called a ray rather than a particle

13 Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General Chemistry, 8th ed., Houghton Mifflin, New York, NY, Majority of figures/tables are from the Ebbing lecture outline. Alpha particles (α) They are known to consist of helium-4 nuclei (nuclei with two protons and two neutrons)They are known to consist of helium-4 nuclei (nuclei with two protons and two neutrons) Positive chargePositive charge Slow movingSlow moving Stopped by small barriers as thin as few pages of paperStopped by small barriers as thin as few pages of paper Symbolized in the following ways:Symbolized in the following ways:

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15 Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General Chemistry, 8th ed., Houghton Mifflin, New York, NY, Majority of figures/tables are from the Ebbing lecture outline. Beta particles (  ) They are known to consist of high speed electrons emitted from the nucleus Negative charge Negative charge Higher speed particles therefore, more penetrating than alpha particles Higher speed particles therefore, more penetrating than alpha particles stopped by only more dense materials such as wood, metal, or several layers of clothing stopped by only more dense materials such as wood, metal, or several layers of clothing The symbol is basically equivalent to an electron The symbol is basically equivalent to an electron

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17 Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General Chemistry, 8th ed., Houghton Mifflin, New York, NY, Majority of figures/tables are from the Ebbing lecture outline. Gamma rays (  ) They have been shown to be a form of electromagnetic radiation (pure energy)They have been shown to be a form of electromagnetic radiation (pure energy) is pure energy (no p, n, e)is pure energy (no p, n, e) Highly energetic, the most penetrating form of radiationHighly energetic, the most penetrating form of radiation barriers of lead, concrete, or more often, a combination is required for protection.barriers of lead, concrete, or more often, a combination is required for protection. Symbol isSymbol is

18 Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General Chemistry, 8th ed., Houghton Mifflin, New York, NY, Majority of figures/tables are from the Ebbing lecture outline.

19 Other Nuclear Particles Neutron Neutron Positron – a positive electron Positron – a positive electron Proton – usually referred to as hydrogen-1Proton – usually referred to as hydrogen-1 Any other elemental isotopeAny other elemental isotope

20 Balancing Nuclear Reactions In the reactants (starting materials – on the left side of an equation) and products (final products – on the right side of an equation) Atomic numbers must balance and Mass numbers must balance Use a particle or isotope to fill in the missing protons and neutrons

21 Nuclear Reactions Alpha emissionAlpha emission Note that mass number (A) goes down by 4 and atomic number (Z) goes down by 2. Nucleons (nuclear particles… protons and neutrons) are rearranged but conserved

22 Nuclear Reactions Beta emissionBeta emission Note that mass number (A) is unchanged and atomic number (Z) goes up by 1.

23 Other Types of Nuclear Reactions Positron ( 0 +1  ): a positive electron Electron capture: Electron capture: the capture of an electron 207

24 Learning Check What radioactive isotope is produced in the following bombardment of boron? 10 B + 4 He ? + 1 n 5 2 0

25 Write Nuclear Equations! Write the nuclear equation for the beta emitter Co-60.

26 Artificial Nuclear Reactions New elements or new isotopes of known elements are produced by bombarding an atom with a subatomic particle such as a proton or neutron -- or even a much heavier particle such as 4 He and 11 B. Reactions using neutrons are called  reactions because a  ray is usually emitted. Radioisotopes used in medicine are often made by  reactions.

27 Artificial Nuclear Reactions Example of a  reaction is production of radioactive 31 P for use in studies of P uptake in the body P n ---> P + 

28 Transuranium Elements Elements beyond 92 (transuranium) made starting with an  reaction U n ---> U +  U ---> Np  Np ---> Pu  Np ---> Pu 

29 Nuclear Fission

30 Nuclear Fission Fission is the splitting of atoms These are usually very large, so that they are not as stable Fission chain has three general steps: 1. Initiation. Reaction of a single atom starts the chain (e.g., 235 U + neutron) 2. Propagation. 236 U fission releases neutrons that initiate other fissions 3. ___________.

31 Stability of Nuclei Out of > 300 stable isotopes: Even Odd Odd Even Z N P 19 9 F 2 1 H, 6 3 Li, 10 5 B, 14 7 N, Ta

32 Band of Stability and Radioactive Decay

33 Representation of a fission process.

34 Nuclear Fission & POWER Currently about 103 nuclear power plants in the U.S. and about 435 worldwide.Currently about 103 nuclear power plants in the U.S. and about 435 worldwide. 17% of the world’s energy comes from nuclear.17% of the world’s energy comes from nuclear.

35 Figure 19.6: Diagram of a nuclear power plant.

36 Nuclear Fusion Fusion small nuclei combine 2 H + 3 H 4 He + 1 n Occurs in the sun and other stars Energy

37 Nuclear Fusion Fusion Excessive heat can not be contained Attempts at “cold” fusion have FAILED. “Hot” fusion is difficult to contain

38 Half-Life HALF-LIFE is the time that it takes for 1/2 a sample to decompose.HALF-LIFE is the time that it takes for 1/2 a sample to decompose. The rate of a nuclear transformation depends only on the “reactant” concentration.The rate of a nuclear transformation depends only on the “reactant” concentration.

39 Half-Life Decay of 20.0 mg of 15 O. What remains after 3 half-lives? After 5 half-lives?

40 Kinetics of Radioactive Decay For each duration (half-life), one half of the substance decomposes. For example: Ra-234 has a half-life of 3.6 days If you start with 50 grams of Ra-234 After 3.6 days > 25 grams After 7.2 days > 12.5 grams After 10.8 days > 6.25 grams

41 Learning Check! The half life of I-123 is 13 hr. How much of a 64 mg sample of I-123 is left after 39 hours?

42 Geiger Counter Used to detect radioactive substances

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44 Radiocarbon Dating Radioactive C-14 is formed in the upper atmosphere by nuclear reactions initiated by neutrons in cosmic radiation 14 N + 1 o n ---> 14 C + 1 H The C-14 is oxidized to CO 2, which circulates through the biosphere. When a plant dies, the C-14 is not replenished. But the C-14 continues to decay with t 1/2 = 5730 years. Activity of a sample can be used to date the sample.

45 Chemotherapy Isotopes of cobalt and radium

46 PET Scans to detect cancer in organs

47 Thyroid Tests Iodine-131

48 Technetium-99 Brain tumor detection and treatments

49 Bone Density Tests (Gd-153) Foodirradiation

50 Plutonium (Pu) Uranium (U) Nuclear Fuels For power plants or nuclear weapons

51 HEALTH EFFECTS OF RADIATION EXPOSURE

52 Decreased white blood cell count Lesions Nausea and diarrhea Birth defects Hair loss Bleeding Death HEALTH EFFECTS OF RADIATION EXPOSURE

53 Effects of Radiation

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55 This is the hand of a physician who was exposed to repeated small doses of x-ray radiation for 15 years. The skin cancer appeared several years after his work with x-rays had ceased. Cancer incidence depends on radiation dose. From Meissner, William A. and Warren, Shields: Neoplasms, In Anderson W.A.D. editor; Pathology, edition 6, St. Louis, 1971, The C.V. Mosby Co

56 Caution: Next slide is the baby one very graphic

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