Learning Objectives:

2. Learning Objectives: • Nuclear reactions result from instability of the nucleus. • Certain combinations of nucleons are inherently unstable, causing some nuclides to undergo radioactive decay. • Types of radioactive decay include alpha emission, beta emission, and gamma emission.

3. Learning Objectives (cont) • Each radioisotope has a characteristic half-life,the time it takes for half of the sample to undergo radioactive decay. • Radioactive dating uses the amount of a radioisotope remaining in a sample to determine its age. • Radioisotopes in the environment contribute to the public’s unavoidable exposure to radiation. • Matter lost during nuclear transformations undergoes conversion to energy.

4. X-rays, the Forerunner to Radioactivity X-rays are a source of pure energy in the form of electromagnetic radiation

5. X ray imageof Bertha Röntgen's hand Credit: Corbis

6. Nuclear vs. Chemical Reactions • Radioisotopes • Atoms that have unstable nuclei are radioactive, meaning that the nucleus may release energy and/or particles to become more stable. • Formation of New Elements • Unlike in chemical reactions, new elements can be formed during nuclear reactions by a process called transmutation. Isotopes are atoms that have different numbers of neutrons but the same Number of protons. Mass number = # protons + # neutrons

7. Atom smashing is like a pool break Credit: Getty Images

8. Search for new Radioactive elements Polonium and Radium Pierre and Marie Curie Credit: Corbis

9. Types of Nuclear Decay: Alpha, Beta, and Gamma Emissions • Alpha-Particle Emission • An alpha particle is identical to a helium-4 nucleus (two protons and two neutrons) • Alpha-particle emission results in a decrease in the atomic number by two and a decrease in the mass number by four.

10. 226Ra  4He + 222Rn 88 2 86 Example B: 240Pu  4He + ? 94 2 240Pu  4He + 236U 94 2 92 Alpha-Particle Emission Example A: 226Ra  4He + ? 88 2

11. Types of Nuclear Decay (cont) • Beta-Particle Emission • A beta particle is identical to an electron. • Results from the conversion of a neutron to a proton and a beta particle • The atomic number increases by one, and the mass number remains the same.

12. 228Ra  0b + 228Ra 214Ra  0b + 214Bi -1 -1 89 83 88 82 Example B: 214Pb  0b + ? 82 -1 Beta-Particle Emission Example A: 228Ra  0b + ? 88 -1 = electron

13. Types of Nuclear Decay • Gamma-Ray Emission • Gamma rays are high-energy electromagnetic radiation only. • There is no change in the identity of an element upon the release of gamma rays.

14. 222Ram 0g + 222Ra 83 0 83 Gamma-Ray Emission Example A: 222Ram 0g + ? 83 0 m stands for metastable

15. Artificial Transmutation • Induced Radioactivity • Bombarding a normally stable nucleus with high-energy particles can lead to transmutation of one element into another. • Transuranic Elements • Elements heavier than uranium (Z=92), the transuranic elements, do not occur in nature but can be made through artificial transmutation.

16. Irène and Frédéric Joliot-Curie Were the 1st to produce a radioactive nuclide through artificial transmutation Credit: Corbis

17. Transuranicelements in the periodic table Elements higher than Uranium 92 are transuranic elements

18. Radioactive Decay • Half-Life • The time required for half a sample to undergo radioactive decay

19. Half-Life

20. A Geiger-Müller counter

21. Geiger-Müller counterwith radioactive antique orange plate

22. Radioactive Decay (cont) • Radioactive Dating • The radioactive decay of carbon-14 can be used to estimate the age of organic materials. Types of Carbon Isotopes 6C12 6C13 6C14 Mass number = # protons + # neutrons

23. The process of Carbon-14 Dating

24. The Shroud of Turin Reputed as the burial cloth of Jesus Christ. C-14 dating by 3 independent labs report the Cloth originated during Medieval times, Between A.D. 1260-1390. Credit: The Image Works

25. Mummified remainsfound frozen in the Italian Alps At least 5000 years old By carbon-14 dating Credit: Landov

26. Radiation Exposure • Background Exposure • Consumer and natural sources such as cosmic rays and radon • Biological Effects of Radiation • Ionizing radiation can lead to damage in both body cells (somatic damage) and reproductive cells (genetic damage). • The penetrating power of the types of radiation follows the general trend: gamma rays > beta particles > alpha particles

27. Sources of radiation

28. Means and result of radon exposure

29. Relative Penetration of Radiation

30. Energy of the Nucleus • Mass-to-Energy Conversion • Mass can be converted to energy during nuclear reactions. • E = mc2. • Binding Energy of a nucleus is • The mass of a nucleus is always less than the sum of the masses of its constituent nucleons. • This mass defect was converted to the “binding energy”, the energy required to dissociate an atom into separate neutrons, protons, and electrons • The energy emitted when separate neutrons, protons, and electrons combine to form an atom. • Equivalent to a quantity of mass expressed by Einstein’s equation, E=mc2

31. Applications of Nuclear Chemistry The study of the chemical effects resulting from the absorption of radiation within living animals, plants, and other materials. Radiation chemistry controls much of radiation biology as radiation has an effect on living things at the molecular scale, to explain it another way, the radiation alters the biochemicals within an organism, the alteration of the biomolecules then changes the chemistry which occurs within the organism, this change in biochemistry can then produce a biological outcome. As a result nuclear chemistry greatly assists in the understanding of medical treatments (such as cancerradiotherapy) and has enabled these treatments to be improved.

32. Radiation therapy (or radiotherapy) is the medical use of ionizing radiation as part of cancertreatment to control malignantcells (not to be confused with radiology, the use of radiation in medical imaging and diagnosis). Radiotherapy may be used for curative or adjuvant cancer treatment. It is used as palliative treatment (where cure is not possible and the aim is for local disease control or symptomatic relief) or as therapeutic treatment (where the therapy has survival benefit but is not curative). Total body irradiation (TBI) is a radiotherapy technique used to prepare the body to receive a bone marrow transplant. Radiotherapy has a few applications in non-malignant conditions, such as the treatment of trigeminal neuralgia, severe thyroid eye disease, pterygium, prevention of keloid scar growth, and prevention of heterotopic ossification. The use of radiotherapy in non-malignant conditions is limited partly by worries about the risk of radiation-induced cancers. Varian Clinac 2100C Linear Accelerator

33. iodine-131 radioactive Dye injected into a Human body Alternative energy sources using nuclear energy, such as nuclear power plants and reactors.

34. Energy of the Nucleus (cont) • Fission • Following splitting (fission) of the uranium-235 nucleus, the masses of the products are less than the masses of the reactants. • The “missing mass” is released as energy. • The Manhattan Project • The Manhattan Project was the code name for the effort to develop a fission-based atomic bomb during World War II.

35. A neutron bombardinga heavy nucleus begins fission The nucleus breaks Into smaller pieces, releasing a lot of energy Fission event is within an atom bomb is initiated by a neutron (gray) bombarding a heavy nucleus such as uranium.

36. 4 Major Research Teams involved in the Manhattan Project • The Metallurgical Laboratory at the University of Chicago ,charged with the creation of a sustained nuclear fission chain reaction. • A laboratory near Knoxville, Tennessee (now known as the Oak Ridge National Laboratory), charged with the enrichment of U-235 • A laboratory in Hanford, Washington, charged with the production, isolation and purification of Pu-239 • A laboratory in Los Alamos, New Mexico, directed by J. Robert Oppenheimer, charged with the design and construction of the atomic bomb.

37. The now-familiarmushroom cloud of the Trinity test Credit: Corbis

38. August 6th, 1945 “Little Boy” dropped on Hiroshima, Japan August 9th, 1945 “Fat Man” dropped on Nagasaki, Japan

39. Nagasaki before (top) and after (bottom) Hiroshima before (top) and after (bottom)

40. Fusion: small nucleiform larger nuclide, release energy This type of Fusion is being Examined as An alternative Energy source On Earth. Small nuclei come together to form larger nuclide, releasing energy

41. Nucleons Radioactive decay Nuclide Radioisotope Transuranic elements X rays Free radical Alpha () particles Beta () particles Gamma () rays Transmutation Positron Half-life Geiger-Müller counter Radioactive dating Somatic damage Genetic damage Strong nuclear force Fission Fusion Mass defect Binding energy Key Words