Protactinium

In 1871, Dmitri Mendeleev, the father of the periodic table predicted that an element existed in between thorium and uranium. The actinide series was not known at that time, but the search for the element was on!

Many experiments were conducted without success. Element 91 was finally identified in 1913 by Kazimierz Fajans and Oswald Helmuth Göhring, when they encountered it during their studies of the decay chains of uranium. They named the element “brevium” because of the short half-life of 1.16 minutes (protactinium-234). In 1917-1918, a more stable isotope (protactinitum-231) was discovered by Lise Meitner and Otto Hahn in collaboration with Frederick Soddy and John Cranston. They chose the name protactinium because they were looking for the “parent” of actinium.

In 1949, the IUPAC chose the name “protactinium” and confirmed Hahn and Meitner as the discoverers. The discovery completed one of the last gaps in early versions of the periodic table.

Protactinium is a very rare, dense, silvery-gray metal. It is malleable and radioactive. It reacts with oxygen, water vapor, and acids. It is a highly toxic and radioactive rare earth metal that requires special handling. Protactinium is a solid. At room temperature it crystallizes in a body-centered tetragonal structure, which can be seen as a distorted lattice.

Because of its scarcity, protactinium is used only in basic scientific research. One isotope, protactinium-231, can be combined with thorium-230 and used to date marine sediments.

Protactinium can form oxides, hydroxides, halides, hydrides, fluorides, bromides, chlorides, iodides, nitrides, and sulfides. Since its oxides are basic, it can easily convert to various salts, such as sulfates, phosphates, and nitrates.

Protactinium has 29 isotopes whose half-lives are known, none of which are stable, with mass numbers 211 to 239. Its longest-lived isotopes are protactinium-231, with a half-life of 32,760 years, protactinium-233 with a half-life of 26.967 days, and protactinium-230 with a half-life of 17.4 days. The remaining isotopes have half-lives shorter than 1.6 days, with the majority of these having half-lives less than 1.8 seconds. All of the isotopes are highly radioactive.

Protactinium occurs naturally in very small amounts in all uranium ores, especially pitchblende. It is also produced as a by-product of uranium processing in nuclear reactors. In its natural state, it is one of the rarest and most expensive naturally occurring elements.

It is found mostly in two isotopes—protoactinium-231 and protoactinium-234. Nearly all naturally occurring protactinium is protactinium-231 (approximately 99.9999%).