[ pruh-mee-thee-uhm ]
/ prəˈmi θi əm /
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a rare-earth, metallic, trivalent element. Symbol: Pm; atomic number: 61.
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Words nearby promethium
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2021
British Dictionary definitions for promethium
/ (prəˈmiːθɪəm) /
a 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 promethium
C20: 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 promethium
[ prə-mē′thē-əm ]
n. Symbol Pm
A 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 promethium
[ prə-mē′thē-əm ]
A 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.