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Chapter 4 Nuclear Chemistry

Chapter 4 Nuclear Chemistry. 4.3 Radiation Measurement 4.4 Half-Life of a Radioisotope 4.5 Medical Applications Using Radioactivity. Radiation Measurement. A Geiger counter detects beta and gamma radiation uses ions produced by radiation to create an electrical current.

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Chapter 4 Nuclear Chemistry

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  1. Chapter 4 Nuclear Chemistry 4.3 Radiation Measurement 4.4 Half-Life of a Radioisotope 4.5 Medical Applications Using Radioactivity

  2. Radiation Measurement A Geiger counter • detects beta and gamma radiation • uses ions produced by radiation to create an electrical current

  3. Radiation Units Units of radiation include: • curie (Ci) - measures activity as the number of atoms that decay in one second • rad (radiation absorbed dose) - measures the radiation absorbed by the tissues of the body • rem (radiation equivalent) - measures the biological damage caused by different types of radiation

  4. Units of Radiation Measurement

  5. Exposure to Radiation Exposure to radiation occurs from • naturally occurring radioisotopes • medical and dental procedures • air travel, radon, and smoking cigarettes

  6. Half-Life The half-life of a radioisotope is the time for the radiation level to decrease (decay) to one-half of the original value.

  7. Decay Curve A decay curve shows the decay of radioactive atoms and the remaining radioactive sample.

  8. Half-Lives of Some Radioisotopes Radioisotopes that are • naturally occurring tend to have long half-lives • used in nuclear medicine have short half-lives

  9. Half-Life Calculations • In one half-life, 40 mg of a radioisotope decays to 20 mg. • After two half-lives, 10 mg of radioisotope remain. 40 mg x 1 x 1 = 10 mg 2 2 1 half-life2 half-lives Initial 40 mg 20 mg 10 mg

  10. Learning Check The half life of I-123 is 13 hours. How much of a 64 mg sample of I-123 remains active after 26 hours? 1) 32 mg 2) 16 mg 3) 8 mg

  11. Solution 2) 16 mg STEP 1Given:64 g; 26 h;13 h/half-life STEP 2Plan: 26 h Number of half-lives STEP 3Equalities: 1 half-life = 13 h STEP 4Set up problem: Number of half-lives = 26 h x 1 half-life = 2 half-lives 13 h 64 mg 32 mg 16 m 13 h 13 h

  12. Medical Applications Radioisotopes with short half- lives are used in nuclear medicine because they • have the same chemistry in the body as the nonradioactive atoms • give off radiation that exposes a photographic plate (scan), giving an image of an organ Thyroid scan

  13. Some Radioisotopes Used in Nuclear Medicine

  14. Learning Check Which of the following radioisotopes are most likely to be used in nuclear medicine? 1) K-40 half-life 1.3 x 109 years 2) K-42 half-life 12 hours 3) I-131 half-life 8 days

  15. Solution Radioisotopes with short half-lives are used in nuclear medicine. 2) K-42 half-life 12 hours 3) I-131 half-life 8 days

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