Definitions

from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. A rare, extremely toxic, radioactive element chemically similar to uranium, having 13 known isotopes, the most common of which is protactinium 231 with a half-life of 32,480 years. Atomic number 91; melting point 1,230°C; specific gravity 15.37; valence 4, 5. See Table at element.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. A chemical element (symbol Pa) with atomic number 91.

from the GNU version of the Collaborative International Dictionary of English

  • The radioactive chemical element, of atomic number 91; Atomic symbol Pa; at. wt. of longest-lived isotope, 231 (T1/2 = 32,500 yrs.) Also called brevium, Uranium X2 and UX2.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • n. a short-lived radioactive metallic element formed from uranium and disintegrating into actinium and then into lead

Etymologies

prot(o)- + actinium (so called because it decays into actinium).
(American Heritage® Dictionary of the English Language, Fourth Edition)
proto- +‎ actinium. (Wiktionary)

Examples

  • An element discovered in 1982 has been named meitnerium to honor Lise Meitner (1878-1968), the Austrian-Swedish physicist and mathematician who discovered the element protactinium and made major contributions to the understanding of nuclear fission.

    Elements

  • Her expertise was on separating protactinium from carnotite and she had previously worked as a consultant for physicians and hospitals. 141

    Trafficking Materials and Gendered Experimental Practices: Radium Research in Early 20th Century Vienna

  • Kudos to moose drool whose handle happens to rhyme with April Fools, too! for the initial protactinium outline.

    New Levels of LEED

  • LEMON cerium germanium gold hafnium iodine iron lanthanum neodymium phosphorus praseodymium protactinium samarium scandium silver sulphur thorium titanium uranium vanadium yttrium zirconium

    Zolar’s Magick Of Color

  • Professor Meitner in 1918, and discovered protactinium, the long-lived mother substance of the actinium series.

    Otto Hahn - Biography

  • However, as U238 decays into its daughter products thorium and protactinium, both beta and gamma radiation are released, increasing the radiation burden further.

    Infowars

  • And gold and protactinium and indium and gallium, (gasp)

    Qulog 2.0

  • Coalesced work from home online jobs, red kindliness, red granger and mastoidal aldol, but postnatal pylon say protactinium to pelvimetry the satiety are reputably way.

    POWET.TV

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