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Applications of Nuclear Chemistry Nuclear Power • huge amount of energy from very little material • zero greenhouse gas emissions • lots of radioactive waste, no long‐term / large‐scale disposal plans • if cooling/containment in nuclear plant is lost, explosion releases deadly radioisotopes into environment Radiometric Dating • 14C is produced naturally in the atmosphere: 147N + 10n ⎯→ 146C + 11H, 1 in ~1012 CO2 molecules is 14CO2 • 14CO2 → plants → animals: all living organisms are have some 14C with t½ = 5730 y • Upon death, no new 14C incorporation, so the fraction of 14C tells you the age of organic material, up to about 50000 years. Other radioisotopes are useful for other timeframes. U‐Th dating, 230Th t½ = 75400 y, used to date corals / limestones up to a few 105 years old K‐Ar and U‐Pb dating, 40K t½ = 1.3 Gyr, 238U t½ = 4.5 Gyr, used to date even the oldest rocks Radioimaging Use radiation emitted from injected radionuclides to image and diagnose bodily function e.g. Positron Emission Tomography (PET) uses 18F‐labelled glucose 0
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9F ⎯→ 8O + 1β, then 1β + –1e ⎯→ 2 0γ emitted 180° apart: detect them for a 3D image of metabolic activity (useful to search for tumours, etc) Radiation Damage • All radiation associated with radionuclides is ionizing radiation, radiation with enough energy to remove electrons from atoms and break bonds in molecules. (X‐rays and UV light are also ionizing.) • Key result: damage to DNA can lead to mutation, mutation can lead to cancer (esp leukemia). • All matter is naturally radioactive, and a certain background level of ionizing radiation is normal, but prolonged or repeated exposure to high levels is dangerous. • Cancer cells grow more rapidly than normal cells, so cancer cells are more susceptible to radiation damage. Many cancer therapies involve external radiation or targeted radioisotopes. Chemistry 121 – Fall 2011 Learning Objectives Addendum – Nuclear Chemistry 1) define the terms radioactivity and nuclide 2) define the belt of stability as it pertains to the neutron:proton ratio of nuclides 3) give the names, charges, and mass numbers of the particles involves in nuclear reactions 4) write balanced equations for nuclear reactions 5) define α‐decay, β‐decay, position emission, and electron capture 6) perform calculations involve half‐lives and rates of radioactive decay 7) define fission and fusion 8) briefly describe some applications of nuclear chemistry Suggested Problems from Petrucci 10/e Chapter 25: 1 9 23 27 43 83 85