Chapter 4 Nuclear Radiation Background image source:

Natural Radioactivity Unstable isotopes Elements with atomic numbers over 84 Repulsion within the nucleus Often written Uranium-238 or U-238 Usually read “Uranium-238” U Mass number Atomic number

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Radiation Alpha (α) particle –He nucleus: 2 protons, 2 neutrons –Heaviest –Charge: 2+ –Least penetrating –Most damaging: electron-hungry! Destroys DNA and proteins –Sources of exposure: heavy metals in soil taken up into plants, smoke detectors, cigarettes

Radiation Beta (β) particle –High-energy electron from unstable nucleus –Insignificant mass –Charge: 1- –More penetrating than α particles –Not as damaging, also ionizing radiation –Sources of exposure: heavy metals in soil taken up into plants, cigarettes Neutron ProtonElectron (β particle)

Radiation Beta (β+) particle –High-energy positron from unstable nucleus –Insignificant mass –Charge: 1+ –More penetrating than α particles –Not as damaging, also ionizing radiation –Sources of exposure: heavy metals in soil taken up into plants, cigarettes Neutron Proton Positron (β+ particle)

Radiation Gamma (γ) Ray –Collection of radiation (energy only) –No mass –No charge –Most penetrating radiation –Least damaging, but most prevalent! –Sources of exposure: medical treatments, industrial processes, sterilization Positron (β+ particle)Electron (β particle) γ Ray

Comparison

Half-Life The amount of time it takes for one half of a sample to decay Ever reaches zero? Decay curve

Try it! Iron-59 has a half-life of 46 days. If the laboratory received a sample of 8.0g Fe- 59, how many grams are still active after 184 days? 0.50g

Radiometric Dating The half-life of an element is used to determine how long ago something lived Element studied in a sample depends on what you need to see! –Fossils: carbon-14 (half-life = 5730 years) –Rocks: potassium-40 (half-life = 1.3 x 10 9 years) –Medical applications: Carbon-11 (half-life = 20 minutes) Potassium-42 (half-life = 12 hours) Iron-59 (half-life = 46 days)

Radiometric Dating

Nuclear Fission Splitting atoms “Missing mass” in products—converted to enormous energy Starts a chain reaction –Sufficient quantities of material in close proximity Great source of power?

Nuclear Fusion Joining atoms More energy required and released than fission Need temperatures of at least 100 million °C “Missing mass” in products—converted to enormous energy Great source of power?

Try it! Complete the following fission reaction: 235 U  131 Sn + ? + energy 104 Mo Complete the following fusion reaction: 2 H + 1 H + energy  ? + ENERGY 3 He

Radiation and You Source:

Radiation and You Radiation is all around us every day— some harmful and some very useful Benefits of radiation Dangers of radiation

Radiation and You Radiation used in war –WWII was ended after Japan was bombed by U.S. forces –Hiroshima: uranium fission bomb –Nagasaki: plutonium fission bomb –Nearly ¼ million died Radioactive fallout –Incorporation into tissues: continuous radiation Source:

Nuclear Power Power Plant Design Source:

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Nuclear Power Is it worth the risk? Source: