1. Uses of Radioactivity

2. Nuclear Fission The splitting of the nucleus of a large atom into two or more fragments The splitting of the nucleus of a large atom into two or more fragments It produces additional neutrons and lots of energy It produces additional neutrons and lots of energy Fission can cause chain reactions – a reaction in which a change in a single molecule makes many molecules change. Fission can cause chain reactions – a reaction in which a change in a single molecule makes many molecules change. Critical Mass – the minimum mass of a fissionable isotope that provides enough neutrons to maintain a chain reaction Critical Mass – the minimum mass of a fissionable isotope that provides enough neutrons to maintain a chain reaction

3. Figure 11 on page 654

4. Chain Reactions are used in Nuclear Reactors

5. Nuclear Fusion The combination of the nuclei of small atoms to form a larger nucleus The combination of the nuclei of small atoms to form a larger nucleus This process also creates energy. This process also creates energy. The sun uses nuclear fusion to generate heat and light. The sun uses nuclear fusion to generate heat and light.

6. Half-Life and Geologic Dating Half-life is the time required for half of a sample of radioactive substance to disintegrate by radioactive decay or natural processes. Half-life is the time required for half of a sample of radioactive substance to disintegrate by radioactive decay or natural processes. So every time the “half-life time” passes, half of the parent substance (original substance) has turned into the daughter substance (new substance) So every time the “half-life time” passes, half of the parent substance (original substance) has turned into the daughter substance (new substance)

7. 1.00 mg A look at half life Iodine-131 has a half-life of 8.02 days. So after 8.02 days, half of the Iodine-131 will have decayed to Xenon-131 0.00 days 0.500 mg0.750 mg0.875 mg 0.125 mg 8.02 days16.04 days24.06 days 0.250 mg0.500 mg 0 half-lives1 half-lives2 half-lives3 half-lives

8. Example Problems Assuming a half life of 1599 years, how many years will be needed for the decay of 15/16 of a given amount of radium-226. Assuming a half life of 1599 years, how many years will be needed for the decay of 15/16 of a given amount of radium-226. The half-life of radon-222 is 3.824 days. How much time must pass for one-fourth of a given amount of radon to remain. The half-life of radon-222 is 3.824 days. How much time must pass for one-fourth of a given amount of radon to remain. The half-life of polonium is 3.0 minutes. If you start with 16 mg of polonium-218, how much time must pass for only 1.0 mg to remain. The half-life of polonium is 3.0 minutes. If you start with 16 mg of polonium-218, how much time must pass for only 1.0 mg to remain.

9. Geologic Dating As you can guess, we can use half-life and radioactive decay to determine the geologic age of materials. As you can guess, we can use half-life and radioactive decay to determine the geologic age of materials. Example: An ancient artifact is found to have a ratio of carbon-14 to carbon-12 that is one-eighth of the ratio of carbon- 14 to carbon-12 found in a similar object today. How old id this artifact? (C-14 has a half life of 5715 years). Example: An ancient artifact is found to have a ratio of carbon-14 to carbon-12 that is one-eighth of the ratio of carbon- 14 to carbon-12 found in a similar object today. How old id this artifact? (C-14 has a half life of 5715 years).

10. Other uses of Nuclear Chemistry Smoke Detectors Smoke Detectors Art Forgeries Art Forgeries Medicinal Reasons Medicinal Reasons –X-rays –PET scans (Positron Emission Tomography)

11. Even though radiation can be helpful, it can be dangerous Large doses of radiation in a short period of time or small doses of radiation over long periods of time can lead to: Large doses of radiation in a short period of time or small doses of radiation over long periods of time can lead to: –Decrease in white blood cells –Nausea –Loss of hair –Ulcers –Internal bleeding –Death