protactinium

[ proh-tak-tin-ee-uhm ]
/ ˌproʊ tækˈtɪn i əm /

noun Chemistry.

a radioactive, metallic element. Symbol: Pa; atomic number: 91.

QUIZZES

BEAT THE DOLDRUMS WITH THIS WORD OF THE DAY QUIZ!

We know you’ll tackle this quiz totis viribus! See how many words from the week of Oct 12–18, 2020 you get right!
Question 1 of 7
What does “Indigenous” mean?

Origin of protactinium

First recorded in 1915–20; prot- + actinium
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2020

British Dictionary definitions for protactinium

protactinium
/ (ˌprəʊtækˈtɪnɪəm) /

noun

a toxic radioactive metallic element that occurs in uranium ores and is produced by neutron irradiation of thorium. Symbol: Pa; atomic no: 91; half-life of the most stable isotope, 231 Pa: 32 500 years; valency: 4 or 5; relative density: 15.37 (calc.); melting pt: 1572°CFormer name: protoactinium
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 protactinium

protactinium
[ prō′tăk-tĭnē-əm ]

n. Symbol Pa

A rare, extremely toxic radioactive element having 13 known isotopes, the most stable of which is Pa 231 with a half-life of 32,700 years. Atomic number 91.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Scientific definitions for protactinium

protactinium
[ prō′tăk-tĭnē-əm ]

Pa

A rare, extremely toxic, radioactive metallic element of the actinide series that occurs in uranium ores. It has 13 known isotopes, the most stable of which is protactinium 231 with a half-life of 32,760 years. Atomic number 91; approximate melting point 1,550°C; specific gravity 15.37; valence 4, 5. See Periodic Table.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.