Chapter 25 Nuclear Chemistry

1. Chapter 25Nuclear Chemistry

2. Chemical vs. Nuclear Reactions Chemical Reactions- A rearrangement of atoms and molecules by breaking and forming bonds -involves electrons Nuclear Reactions- Combining, splitting or decay the nuclei of atoms.

3. Nuclear Chemistry involves the NUCLEUS of the atom. That means…. the protons and neutrons will undergo a change (nuclear reactions) Nuclear reactions usually involve radioactive elements

4. Radioactive Elements are NOT stable…. …because of the proton to neutron ratio.

5. Radioactivity & Radiation - Alpha, Beta, Gamma - YouTube

6. Radioactive elements will give off particles and energy until they become stable (non-radioactive)

7. Radioactive elements change by themselves Of the 119+ different atoms…. …there are more than 1500 different nuclei, only 264 are stable

8. Discovery of Radioactivity Professor Roentgen – 1895- found that certain elements gave off X-rays but didn’t know what caused them.

9. Antoine Henri Bacquerel • 1896 • exposed a uranium-bearing crystal to sunlight • then placed it on a photographic plate the crystal produced an image

10. Bacquerel theorized… …..that the absorbed energy of the sun was being released by the uranium in the form of x-rays This theory was proven incorrect because when he didn’t expose it to light, he still got the image

11. Since the crystal produced its own image on the plate without being expose to sunlight, he theorized that the crystal produced its own rays.

12. HowStuffWorks Videos "100 Greatest Discoveries: Radioactivity"

13. Marie and Pierre Curie -Marie Curie (1867-1943) and Pierre Curie (1859-1906)

14. -They found that uranium gave off particles from the nucleus- (shown by a change in mass) -Won Nobel Prize in 1903 for this research

15. Next they…… • Studied pure uranium vs. ore containing uranium • ore was more radioactive than the pure material. • Conclusion: ore contained additional radioactive components besides the uranium. • This observation led to the discovery of two new radioactive elements, polonium and radium.

16. -Marie won 2nd Nobel Prize in 1911 for finding the radioactive elements polonium and radium.

17. 1910 In honor of Marie and Pierre Curie……the Radiology Congress chose the curie as the basic unit of radioactivity

18. -Marie organized first mobile x-ray machines to be used in World War I

19. -Marie pioneered use of radiation in cancer treatment -Marie died of leukemia in 1943.

20. Ernest Rutherford (1871-1937) • father of nuclear physics. • Particles named and characterized by him include the alpha particle, beta particle and proton.

21. Nuclear Science • Began with Albert Einstein • E = mc2 • Energy= mass x (speed of light)2 • Speed of light - 299,792,458 m/s (meters per second) or 186,000miles/second or 671 million miles/hr. (around earth in 1.3 seconds) • very small amounts of mass may be converted into a very large amount of energy

22. The Case of the Doomed Dial Painters

23. In 1917, pretty Florence Kohler Casler was happily engaged in her first job. At the U.S. Radium Corporation’s plant in Orange, NJ, she sat by a table covered with watch dials. Tipping a tiny brush continuously with her tongue, she coated their numerals with luminous paint containing tiny amounts of radium. Two years later she quit and got married. In 1949, cancer developed in her sinuses. Last week, Florence Casler died, the 41st victim of the famous radium poisoning of the 1920’s. • LIFE Magazine, December, 1951.

24. Radium watch dial painters

25. In 1917, many young women working for the United States Radium Corporation thought they had found the perfect job. Wages were good and the work was easy. As watch dial painters, all they had to do was mix up a batch of glow-in–the-dark radium based paint and brush the paint on the watch dials. In order to apply the paint precisely, they were encouraged to “sharpen” the points of the brushes with their tongues.

28. At the time, radium- based glow-in-the-dark paint was a popular gimmick. People loved watches they could read in the dark. Some of the workers even painted their nails with it or sprinkled it in their hair. No one ever told them it was deadly.

29. In the early 1920s, however the dial painters started getting sick. The women began losing their teeth and suffering from gum ulcers, anemia, tumors and “jaw rot” – a painful decay of bone and tissue in the mouth. By 1924, 50 women were ill and a dozen had died.

30. Doctors and dentists were mystified. An increasing number of seemingly healthy young women were developing terrible symptoms and the only thing the women had in common was the fact that they had all worked at the same job for the United States Radium Corporation.

32. NOT US ! Authorities at the New Jersey Department of Labor failed to identify anything hazardous at the work site. The United States Radium Corporation accepted no responsibility, claiming that the women’s ills were due to “poor dental habits” or in the words of the company’s president, “a hysterical condition brought about by coincidence”. But some people suspected that radium was the cause.1

33. THE PLOT THICKENS In 1925, Dr. Harrison S. Martland, the Medical Examiner of Essex County, was asked to investigate the death of a 36 year old man, who was employed as a chemist by the United States Radium Corporation. The man, who had been diagnosed with anemia, presented Dr. Martland with a puzzling situation. For a case of normal anemia, death had come much too quickly.2

34. Dr. Martland was intrigued. He consulted with an expert on radiation, Dr. Sabin A. Von Sochocky, a founder of the United States Radium Corporation and the inventor of the radium paint the workers had been using. Together, they analyzed tissue and bone from the chemist who had died. The results were startling. The chemist’s body was saturated with radioactivity! Dr. Martland and Dr. Von Sochocky suspected that others who had worked at the factory were contaminated, too.3

35. SOLVING THE MYSTERY Dr. Martland and his team built a radiation detector (somewhat like a Geiger counter) and tested one of the dying dial painters. When she breathed into their detector, they saw that she was filled with radioactivity.

36. After the dial painter died, Dr.Martland removed a splinter of bone from her body. When he strapped a paper clip, a broken blade and dental x-ray film to the dead woman’s leg, her bone had absorbed so much radium that it emitted enough radiation to expose the film and silhouette the bits of metal.

37. Dr. Martland tested other painters. Whether they appeared healthy or sick, they were all radioactive. Von Sochocky tested himself and discovered that his breath contained higher levels of radioactivity than anyone else tested. He subsequently died “a horrible death”.4 (Aplastic anemia)

38. On December 5, 1925, Dr. Martland presented his finding in The Journal of the American Medical Association. For the first time, the deadly effects of radiation had been clearly established.5 • 1 Marc Mappen.”Jerseyana”. The New York Times, March 10, 1991, Sunday Late edition, Section12NJ,p.13 • 2 Ibid • 3Ibid • 4Ibid • 5Ibid

39. Radioactivity -the process in which an unstable atom emits charged particles and energy to become a stable atom proton to neutron ratio determines what type of radiation is given off Substances that give off particles from the nucleus are radioactive.

40. Only certain isotopes (nuclides) are radioactive • Nuclide- a specific nucleus • Nuclides that are radioactive are called radioisotopes

41. Radioisotopes (unstable atoms) -atoms with more than 83 protons are usually unstable

42. Transuranium Elements • The elements past uranium (#92) • All radioactive

43. Showing Radioactive Atoms. Use Isotope Notation C-12 C-14 Mass number 12 14 C C 6 6 Atomic number

44. To become stable, radioisotopes give off radiation (Radioactive decay) radiation Unstable atom

45. Types of Radiation • Alpha Particle: α • Beta Particle: β • Gamma Ray: γ

46. Alpha Decay -when an atom gives off an alpha particle Alpha Particle = 2p and 2n -atomic # goes down 2 and atomic mass goes down 4

47. Alpha Decay

49. Written as: 4 He (in nuclear equations) 2 or a (in decay series)

50. -U-238 turns into Th-234 when it gives off an alpha particle Ex. (nuclear equation) 238 4 234 U Th He + 90 92 2