| 词汇 | example_english_astatine |
| 释义 | Examples of astatineThese examples are from corpora and from sources on the web. Any opinions in the examples do not represent the opinion of the Cambridge Dictionary editors or of Cambridge University Press or its licensors. She discovered that the element 85 astatine is a product of the natural decay processes. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. Accordingly, much less is known about astatine than most other elements. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. Four out of these isotopes (astatine-215, astatine-217, astatine-218, and astatine-219) are found due to their production in major natural decay chains. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. The least stable ground state isotope is astatine-213, with a half-life of 125 nanoseconds. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. Even though heavier astatine isotopes release less energy, no long-lived astatine isotope exists, due to the increasing role of beta decay (electron emission). From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. All of its isotopes are short-lived; the most stable is astatine-210, with a half-life of 8.1 hours. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. There are 32 known isotopes of astatine, with atomic masses (mass numbers) of 191 and 193223. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. Astatine, which is usually classified as a nonmetal or a metalloid, has been predicted to have a metallic crystalline structure. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. Francium is a highly radioactive metal that decays into astatine, radium, and radon. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. While hydroiodic acid solutions are stable, the hydronium-astatide solution is clearly less stable than the water-hydrogen-astatine system. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. Astatine may be dark, or it may have a metallic appearance and be a semiconductor, or it may even be a metal. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. The properties he reported for dakin do not correspond to those of astatine, and the true identity of dakin is not known. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. A visible piece of astatine would be immediately and completely vaporized due to the heat generated by its intense radioactivity. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. The least stable one is astatine-214m1; its half-life of 265 nanoseconds is shorter than those of all ground states except that of astatine-213. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. Astatine-219 decays to polonium-215, which itself beta decays to astatine-215 with an even smaller probability of 0.00023%. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. She became provisional director of the institute in 1945 and official in 1947 upon discovering the existence of astatine. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. In 2013, on the basis of relativistic modelling, astatine was predicted to be a monatomic metal, with a face-centred cubic crystalline structure. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. Elements less commonly recognised as metalloids include carbon, aluminium, selenium, polonium and astatine. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. The chemistry of astatine in aqueous solution is mainly characterised by the formation of various anionic species. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. In 1950 astatine was described as a halogen and (therefore) a reactive nonmetal. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. However, there are three naturally occurring radioactive isotopes of astatine produced via radioactive decay of uranium, neptunium, and plutonium. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. Astatine is not well-studied, and although there is a report of a non-volatile astatine monofluoride, its existence is debated. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. Beta decay modes have been found for all astatine isotopes except astatine-213, astatine-214, astatine-215, and astatine-216m. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. The newly formed astatine-211 is important in nuclear medicine. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. Astatine is usually classified as either a nonmetal or a metalloid. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. The bulk properties of astatine are not known with any great degree of certainty. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. In a manner similar to iodine, astatine is preferentially concentrated in the thyroid gland, although to a lesser extent. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. A beta decay mode has been found for all astatine isotopes except for astatine-213, astatine-214, astatine-215, and astatine-216m. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. The least stable ground state isotope is astatine-213, with a half-life of about 125 nanoseconds. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. Unlike its lighter congenor iodine, evidence for diatomic astatine is sparse and unconfirmed. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. Beginning with naturally occurring uranium-238, this series includes the following elements: astatine, bismuth, lead, polonium, protactinium, radium, radon, thallium, and thorium. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. In contrast, astatine, the second-least stable naturally occurring element, has a half-life of 8.5 hours. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. There are no stable isotopes of astatine. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. On a standard periodic table all of these elements can be found in a diagonal region of the p-block, extending from boron at one end to astatine at the other. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. Once produced, astatine must be used quickly, as it decays with a half-life of 7.2 hours; this is, however, long enough to permit multi-step labeling strategies. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. Early research suggested that injection of lethal quantities of astatine caused morphological changes in breast tissue (although not other tissues); however, this conclusion currently remains controversial. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. Astatine forms covalent compounds with non-metals. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. All isotopes of francium decay into either astatine, radium, or radon. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. Interestingly, the lowest element in this group is also a highly radioactive and rare element, astatine. The actual properties of astatine remain a mystery to us, but we could make a good guess at some of them. Astatine's alpha decay energies follow the same trend as for other heavy elements. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. Depending on the author, one or more from selenium, polonium or astatine are sometimes added to the list. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. The inclusion of antimony, polonium and astatine as metalloids has also been questioned. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. Iodine and astatine only partially react with hydrogen, forming equilibria. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. The most important isotope is astatine-211, the only one to currently have a commercial use. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. Lighter astatine isotopes have quite high energies of alpha decay, which become lower as the nuclei become heavier. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. The two following isotopes release even more energy, with astatine-213 releasing the highest amount of energy of all astatine isotopes. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. Astatine is only produced in microscopic quantities, with modern techniques allowing production runs of 2 terabecquerels (about 25 micrograms). From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. As such, astatine could be expected to have a metallic appearance; show metallic conductivity; and have excellent ductility, even at cryogenic temperatures. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. Astatine is commonly regarded as a nonmetal, less commonly as a metalloid and occasionally as a metal. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. Several authors have commented on the metallic nature of some of the properties of astatine. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. Germanium forms tetrahalides with all halogens except astatine and forms dihalides with all halogens except bromine and astatine. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. Tin forms dihalides and tetrahalides with all halogens except astatine. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. These examples are from corpora and from sources on the web. Any opinions in the examples do not represent the opinion of the Cambridge Dictionary editors or of Cambridge University Press or its licensors. |
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