Bell Work 1. Is all radiation bad? Justify your answer. 2. What is a fissure? 3. What does it mean to fuse something together? 4. What is a chain reaction? 5. What are some uses of radiation that you can think of? 6. Update your scientist timeline paper with Henri Becquerel and Pierre and Marie Curie

Questions?

Reality Check ½ sheet of paper ½ sheet of paper Extra credit if you can tell me : Extra credit if you can tell me : –The type of radioactive particle –Was it emitted or captured?

Reality Check 2.5Name: Block: Supply the missing information in the following nuclear equations: 1) Na  Ne + ________ 2) Tl  He + ________ 3)__________ + e  Rn 4) Ac  e + _____________ 5)_______ + He  Pb

Uses of Radioactivity

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

Figure 11 on page 654

Chain Reactions are used in Nuclear Reactors

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.

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)

Example Problems Amount remaining = Amount original (1/2) Total Time/Half Life 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. The half-life of radon-222 is days. How much time must pass for one-fourth of a given amount of radon to remain. The half-life of radon-222 is days. How much time must pass for one-fourth of a given amount of radon to remain. Assuming a half life of 1599 years, how much radium will remain after 9594 years if the original amount was 900 grams? Assuming a half life of 1599 years, how much radium will remain after 9594 years if the original amount was 900 grams? What is the half life of a material if 1/8 of the material remains after 16 years? What is the half life of a material if 1/8 of the material remains after 16 years?

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).

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

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

Homework Page 670: Page 670: 37-42