| 单词 | promethium |
| 释义 | promethium[ pruh-mee-thee-uhm ] / prəˈmi θi əm / noun Chemistry.a rare-earth, metallic, trivalent element. Symbol: Pm; atomic number: 61. Origin of promethiumFrom New Latin, dating back to 1945–50; see origin at Prometheus, -ium Words nearby promethiumPromethea moth, Promethean, Prometheus, Prometheus Bound, Prometheus Unbound, promethium, promilitary, prominence, prominent, prominent heel, prominent moth Dictionary.com UnabridgedBased on the Random House Unabridged Dictionary, © Random House, Inc. 2020 British Dictionary definitions for promethiumpromethium / (prəˈmiːθɪəm) / nouna radioactive element of the lanthanide series artificially produced by the fission of uranium. Symbol: Pm; atomic no: 61; half-life of most stable isotope, 145 Pm: 17.7 years; valency: 3; melting pt: 1042°C; boiling pt: 2460°C (approx.) Word Origin for promethiumC20: New Latin from Prometheus Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012 Medical definitions for promethiumpromethium [ prə-mē′thē-əm ] n. Symbol PmA radioactive rare-earth element prepared by fission of uranium. Pm 145 is the longest-lived isotope with a half-life of 17.7 years. Atomic number 61. The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company. Scientific definitions for promethiumpromethium [ prə-mē′thē-əm ] PmA radioactive metallic element of the lanthanide series. Promethium does not occur in nature but is prepared through the fission of uranium. It has 17 isotopes, one of which is used to make long-lived miniature batteries that work at extreme temperatures for up to five years. The longest-lived isotope, Pm 147, has a half-life of 2.5 years and is used as a source of beta rays. Atomic number 61; melting point 1,168°C; boiling point 2,460°C; valence 3. See Periodic Table. The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved. |
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