Chapter 11 Nuclear Chemistry John Singer, Jackson Community College Chemistry for Changing Times, Thirteenth Edition Lecture Outlines © 2013 Pearson Education, Inc.

2 Chapter 11 © 2013 Pearson Education, Inc. Background Radiation Three-fourths of all exposure to radiation comes from background radiation. Most of the remaining one-fourth comes from medical irradiation such as X-rays.

3 Chapter 11 © 2013 Pearson Education, Inc. Radiation Damage to Cells Nuclear radiation is capable of removing electrons from molecules to from ions in cells, hence the term ionizing radiation. Molecules can also splinter into neutral fragments called free radicals. Free radicals can disrupt cellular processes.

4 Chapter 11 © 2013 Pearson Education, Inc. Radiation Damage to Cells Radiation often affects the fastest growing cells and tissues such as white blood cells and bone marrow. Ionizing radiation can also disrupt DNA causing mutations.

5 Chapter 11 © 2013 Pearson Education, Inc. Radiation Damage to Cells

6 Chapter 11 © 2013 Pearson Education, Inc. Nuclear Equations In nuclear equations, we balance nucleons (protons and neutrons). The atomic number (number of protons) and the mass number (number of nucleons) are conserved during the reaction.

7 Chapter 11 © 2013 Pearson Education, Inc. Nuclear Equations Alpha Decay

8 Chapter 11 © 2013 Pearson Education, Inc. Nuclear Equations Beta Decay

9 Chapter 11 © 2013 Pearson Education, Inc. Nuclear Equations

10 Chapter 11 © 2013 Pearson Education, Inc. Positron emission: A positron is a particle equal in mass to an electron, but with opposite charge. Nuclear Equations

11 Chapter 11 © 2013 Pearson Education, Inc. Electron capture: A nucleus absorbs an electron from the inner shell. Nuclear Equations

12 Chapter 11 © 2013 Pearson Education, Inc. Nuclear Equations

13 Chapter 11 © 2013 Pearson Education, Inc. Nuclear Equations

14 Chapter 11 © 2013 Pearson Education, Inc. Nuclear Equations

15 Chapter 11 © 2013 Pearson Education, Inc. Half-Life The half-life of a radioactive sample is the time required for ½ of the material to undergo radioactive decay.

16 Chapter 11 © 2013 Pearson Education, Inc. Half-Life

17 Chapter 11 © 2013 Pearson Education, Inc. Half-Life Fraction remaining = 1/2 n

18 Chapter 11 © 2013 Pearson Education, Inc. Radioisotopic Dating

19 Chapter 11 © 2013 Pearson Education, Inc. Radioisotopic Dating Carbon-14 dating: The half-life of carbon-14 is 5730 years. Carbon-14 is formed in the upper atmosphere by the bombardment of ordinary nitrogen atoms by neutrons from cosmic rays.

20 Chapter 11 © 2013 Pearson Education, Inc. Radioisotopic Dating Tritium dating: Tritium is a radioactive isotope of hydrogen. It has a half-life of years and can be used for dating objects up to 100 years old.

21 Chapter 11 © 2013 Pearson Education, Inc. Artificial Transmutation Bombardment of stable nuclei with alpha particles, neutrons, or other subatomic particles can cause new elements to form. This process is known as artificial transmutation.

22 Chapter 11 © 2013 Pearson Education, Inc. Uses of Radioisotopes Tracers Radioisotopes can be easily detected through their decay products; therefore, isotope movement can be traced. Some uses of tracers include: Detect leaks in underground pipes. Determine frictional wear in piston rings. Determine uptake of phosphorus and its distribution in plants.

23 Chapter 11 © 2013 Pearson Education, Inc. Uses of Radioisotopes Irradiation of Food Radioisotopes can destroy microorganisms that cause food spoilage.

24 Chapter 11 © 2013 Pearson Education, Inc. Nuclear Medicine Radiation therapy: Nuclear radiation can be used to kill cancerous cells. Radiation is most lethal to fastest growing cells. Radiation is aimed at the cancerous tissue. Patients undergoing radiation therapy often experience nausea and vomiting, which are early signs of radiation sickness.

25 Chapter 11 © 2013 Pearson Education, Inc. Nuclear Medicine Diagnostic Uses of Radiation

26 Chapter 11 © 2013 Pearson Education, Inc. Nuclear Medicine Gamma ray imaging: Technetium-99m emits gamma radiation. It can be used to image the heart and other organs and tissues.

27 Chapter 11 © 2013 Pearson Education, Inc. Nuclear Medicine Positron Emission Tomography (PET): A patient inhales or is injected with positron-emitting isotopes such as carbon-11 or oxygen-15. When positrons encounter electrons, they emit two gamma rays, which exit the body in opposite directions. PET scans can be used to image dynamic processes.

28 Chapter 11 © 2013 Pearson Education, Inc. Penetrating Power of Radiation Alpha radiation is least penetrating and cannot penetrate the outer layer of skin. Alpha radiation is stopped by a sheet of paper. Beta radiation can penetrate through a few cm of skin and tissue. Beta radiation is stopped by a sheet of aluminum foil. Gamma radiation will pass right through a body. Gamma radiation requires several cm of lead to stop.

29 Chapter 11 © 2013 Pearson Education, Inc. Penetrating Power of Radiation

30 Chapter 11 © 2013 Pearson Education, Inc. Two means of protecting one’s self from radiation are distance and shielding. Distance: Move away from the source. The intensity of radiation decreases with increasing distance from the source. Shielding: Lead is a commonly used shield for radiation. Penetrating Power of Radiation

31 Chapter 11 © 2013 Pearson Education, Inc. Energy from the Nucleus By 1905, Albert Einstein had developed his famous mass–energy equation: E = mc2E = mc2 E = Energy m = Mass c = Speed of light

32 Chapter 11 © 2013 Pearson Education, Inc. Energy from the Nucleus When protons and neutrons combine to form a nucleus, a small amount of mass is converted into energy. This is known as binding energy.

33 Chapter 11 © 2013 Pearson Education, Inc. Binding Energy

34 Chapter 11 © 2013 Pearson Education, Inc. The Building of the Bomb Nuclear fission: Fission occurs when larger nuclei split into small nuclei.

35 Chapter 11 © 2013 Pearson Education, Inc. Nuclear Chain Reaction Fission of one nucleus produces neutrons that can cause the fission of other nuclei, thus setting off a chain reaction.

36 Chapter 11 © 2013 Pearson Education, Inc. Manhattan Project The Manhattan Project was launched by President Roosevelt in It consisted of four separate research teams attempting to: Sustain the nuclear fission reaction Enrich uranium Make fissionable plutonium-239 Construct a fission atomic bomb

37 Chapter 11 © 2013 Pearson Education, Inc. Manhattan Project Atomic Bomb

38 Chapter 11 © 2013 Pearson Education, Inc. Manhattan Project Mushroom cloud over Nagasaki from the detonation of “Fat Man,” August 9, 1945.

39 Chapter 11 © 2013 Pearson Education, Inc. Radioactive Fallout Many radioactive isotopes are produced in a nuclear bomb blast. Some are particularly harmful to humans. Among these are strontium- 90 and iodine-131. Strontium-90: Has a half-life of 28.5 years and is chemically similar to calcium. Strontium-90 can be ingested form contaminated dairy and vegetable products and accumulates in bone. Iodine-131: Has a half-life of 8 days. It concentrates in the thyroid glands.

40 Chapter 11 © 2013 Pearson Education, Inc. Nuclear Power Plants Civilian nuclear power plants use uranium that is less enriched uranium-235 ( % uranium-235 rather than 90% for weapons). The nuclear chain reaction is controlled for the slow release of heat energy. The heat is used to make steam, which turns a turbine to produce electricity.

41 Chapter 11 © 2013 Pearson Education, Inc. Thermonuclear Reactions Nuclear fusion is a thermonuclearreaction in which smaller atomic nuclei are fused into larger nuclei. Fusion is the principle reaction in the sun.

42 Chapter 11 © 2013 Pearson Education, Inc. The Nuclear Age