Technetium | Wikipedia audio article
Channel: wikipedia tts
Date: 2018-12-25

This is an audio version of the Wikipedia Article:
https://en.wikipedia.org/wiki/Technetium


00:02:01 1 History
00:02:10 1.1 Search for element 43
00:02:51 1.2 Early misidentifications
00:03:15 1.3 Irreproducible results
00:04:22 1.4 Official discovery and later history
00:07:05 2 Characteristics
00:07:14 2.1 Physical properties
00:08:17 2.2 Chemical properties
00:09:45 3 Compounds
00:09:54 3.1 Pertechnetate and derivatives
00:11:41 3.2 Other chalcogenide derivatives
00:12:22 3.3 Simple hydride and halide complexes
00:15:10 3.4 Coordination and organometallic complexes
00:15:55 3.5 Isotopes
00:16:06 4 Occurrence and production
00:17:15 4.1 Fission waste product
00:18:39 4.2 Fission product for commercial use
00:20:08 4.3 Waste disposal
00:21:15 4.4 Neutron activation
00:23:49 4.5 Particle accelerators
00:29:23 5 Applications
00:30:48 5.1 Nuclear medicine and biology
00:31:53 5.2 Industrial and chemical
00:32:03 6 Precautions
00:32:29 7 Notes
00:32:39 8 References
00:33:22 9 Bibliography
00:33:31 10 Further reading
00:33:44 11 External links
00:34:58 Industrial and chemical
00:35:09 Technetium-99 decays almost entirely by beta decay, emitting beta particles with consistent low energies and no accompanying gamma rays. Moreover, its long half-life means that this emission decreases very slowly with time. It can also be extracted to a high chemical and isotopic purity from radioactive waste. For these reasons, it is a National Institute of Standards and Technology (NIST) standard beta emitter, and is used for equipment calibration. Technetium-99 has also been proposed for optoelectronic devices and nanoscale nuclear batteries.Like rhenium and palladium, technetium can serve as a catalyst. In processes such as the dehydrogenation of isopropyl alcohol, it is a far more effective catalyst than either rhenium or palladium. However, its radioactivity is a major problem in safe catalytic applications.When steel is immersed in water, adding a small concentration (55 ppm) of potassium pertechnetate(VII) to the water protects the steel from corrosion, even if the temperature is raised to 250 °C (523 K). For this reason, pertechnetate has been used as an anodic corrosion inhibitor for steel, although technetium's radioactivity poses problems that limit this application to self-contained systems. While (for example) CrO2−4 can also inhibit corrosion, it requires a concentration ten times as high. In one experiment, a specimen of carbon steel was kept in an aqueous solution of pertechnetate for 20 years and was still uncorroded. The mechanism by which pertechnetate prevents corrosion is not well understood, but seems to involve the reversible formation of a thin surface layer (passivation). One theory holds that the pertechnetate reacts with the steel surface to form a layer of technetium dioxide which prevents further corrosion; the same effect explains how iron powder can be used to remove pertechnetate from water. (Activated carbon can also be used for the same purpose.) The effect disappears rapidly if the concentration of pertechnetate falls below the minimum concentration or if too high a concentration of other ions is added.As noted, the radioactive nature of technetium (3 MBq/L at the concentrations required) makes this corrosion protection impractical in almost all situations. Nevertheless, corrosion protection by pertechnetate ions was proposed (but never adopted) for use in boiling water reactors.
00:37:38 Technetium plays no natural biological role and is not normally found in the human body. Technetium is produced in quantity by nuclear fission, and spreads more readily than many radionuclides. It appears to have low chemical toxicity. For example, no significant change in blood formula, body and organ weights, and food consumption could be detected for rats which ingested up to 15 µg of technetium-99 per gram of food for several weeks. The radiological toxicity of technetium (per unit of mass) is a function of compound, type of radiation for the isotope in question, and the isotope's half-life.All isotopes of technetium must be handled carefully. The most common isotope, technetium-99, is a weak beta emitter; such radiation is stopped by the walls of laboratory glassware.  The primary hazard when working with technetium is inhalation of dust; such radioactive contamination in the lungs can pose a significant cancer risk. For most work, careful handling in a fume hood is sufficient, and a glove box is not needed.



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