protactinium

The element protactinium is a dense, radioactive, silvery-gray metal in the actinide series with atomic number 91 and the symbol Pa. Due to its rarity and its radioactivity, it has no applications outside of research.

The element was first discovered by Kazimierz Fajans and Oswald Helmuth Göhring in 1913, and they dubbed it brevium, with the symbol Bv, due to its short half-life.

But in 1918 Lise Meitner and Otto Hahn discovered a more stable isotope of the element, dubbing it protactinium (pro[t]- + actinium) because one of its decay products is the element actinium:

Die Vermutung, daß die Pechblenderückstände das geeignete Versuchsmaterial bieten, hat sich bewährt. Es ist uns gelungen, ein neues aktives Element aufzufinden und den Beweis zu erbringen, daß es die Muttersubstanz des Actiniums ist. Wir schlagen dafür den Namen Protactinium vor.

[The assumption that the pitchblende residues provide suitable experimental material has been confirmed. We have succeeded in finding a new active element and providing evidence that it is the parent substance of actinium. We propose the name protactinium for it.]

In early use, the name protoactinium was occasionally used, taking the added < t > to mean the prefix was proto- instead of pro-

In 1949, the International Union of Pure and Applied Chemistry (IUPAC) gave priority of discovery to the Hahn and Meitner, and hence protactinium is the name used today.

Sources:

Fajans, Kasimir and Paul Beer. “Das Verhalten der Radio-elemente bei Fällungsreaktionen.” Berichte der Deutschen Chemischen Gesellschaft, 46.3, July 1913, 3486–97 at 3492. DOI: 10.1002/cber.191304603130.

Hahn, Otto von and Lise Meitner. “Die Muttersubstanz des Actiniums, ein Neues Radioaktives Element von Langer Lebensdauer.” Physikalische Zeitschrift, 19.10, 15 May 1918, 208–18 at 211. HathiTrust Digital Library.

Hevesy, G. v. “Diffusion und Valenz der Radioelemente” (7 October 1913). Physikalische Zeitschrift, 14.24, 1 December 1913, 1202–09 at 1205. HathiTrust Digital Archive.

Miśkowiec, Pawel. “Name Game: The Naming History of the Chemical Elements—Part 3—Rivalry of Scientists in the Twentieth Century.” Foundations of Chemistry, 12 November 2022. DOI: 10.1007/s10698-022-09452-9.

Oxford English Dictionary, third edition, June 2007, s.v. protactinium, n.

Photo credit: Unknown photographer, 1969. US Department of Energy photo. Flickr.com. Wikimedia Commons. Public domain image.