An eye for an i #451 Children

The meitnerium mystery

Memorial erected in 2014 in the Court of Honor of the Humboldt University in Berlin shows nuclear physicist Lise Meitner .   | Photo Credit: Kvikk/ Wikimedia Commons

Just like transuranium elements correspond to the chemical elements with atomic number greater than 92 (the atomic number of uranium), transfermium elements are those elements that have an atomic number greater than 100 (the atomic number of fermium). Even though transfermium elements are a subset of transuranium elements, which are all unstable and decay radioactively into other elements, the need for this classification stems from a number of reasons.

Apart from the fact that none of the transfermium elements occur naturally and are all synthesised artificially, sometimes with great difficulty, they are also united in the fact that very little is still known about these elements, as only a few atoms of each have been produced so far.

Transfermium Wars

One other factor that is common to these elements is the well-documented tussle between the Cold War adversaries over the discovery priority and naming of many of the transfermium elements. Even dubbed as the transfermium Wars, it draws attention to the furious bickering over these elements, mainly involving the Lawrence Berkeley National Laboratory in the U.S. and the Joint Institute of National Research in Dubna.

Founded in Darmstadt in what was then West Germany in 1969, the Gesellschaft fur Schwerionenforschung (GSI Helmholtz Centre for Heavy Ion Research), which was the German nuclear research facility, emerged as a new player in synthesis of super-heavy elements. Led by German physicists Peter Armbruster and Gottfried Munzenberg, the team first tasted success in 1981 with the discovery of element 107.

A single atom of meitnerium

And then, on August 29, 1982, they succeeded again when they produced a single atom of meitnerium. The element was synthesised by bombarding a target of bismuth-209 with accelerated nuclei of iron-58, yielding a single atom of what came to be known as meitnerium. The isotope produced, meitnerium-266, had 157 neutrons in its nucleus along with 109 protons, which defines the element and gives it its atomic number.

Electron shell diagram of meitnerium.

Electron shell diagram of meitnerium.   | Photo Credit: Pumbaa Greg Robson Wikimedia Commons

Even though the International Union of Pure and Applied Chemistry (IUPAC) had stepped in by this time to clearly state that scientists should avoid prematurely suggesting names for new elements that were then mired in controversy and disputes, meitnerium escaped unscathed as no other team claimed priority for its discovery. The GSI group named it after nuclear physicist Lise Meitner and it was formally accepted in 1997 by IUPAC.

“Render justice”

Armbruster had described the naming as a way “to render justice to a victim of German racism and to credit in fairness a scientific life and work”. For Meitner not only faced discrimination as a woman, but also as a Jew and had to flee Germany. What’s worse, her instrumental role in the discovery of nuclear fission didn’t receive due credit as she was marginalised by German chemist Otto Hahn, her long-term collaborator and someone she had seen as a friend.

While Hahn was awarded the Nobel Prize in Chemistry in 1944 “for his discovery of the fission of heavy nuclei”, Meitner’s contributions were neglected. Meitner herself described Hahn’s behaviour in her biography Lise Meitner: A Life in Physics as “simply suppressing the past”, before adding that “I am part of that suppressed past”.

Meitner did receive some recognition for her works before her death in 1968 and her exclusion from the Nobel Prize is now widely considered as unfair. Her scientific contributions were forever immortalised when the name meitnerium was officially adopted for element 109 in 1997. After all, fewer chemists have an element named after them than those who have won the Nobel Prize.

Short half-life

While practical applications of meitnerium would probably make both the element and the woman it is named after more famous, it is clearly something for the future. The original method used to produce an atom in 1982 was repeated in 1988 and 1997, producing two and 12 atoms, respectively. While a number of other isotopes of meitnerium have also been reported, all of these have half-lives ranging from milliseconds to a few seconds at the most.

The limited availability of the element, both in terms of quantities and time, implies that studying it has been extremely difficult, even using experimental techniques that are collectively known as atom-at-a-time methods.

Even though the element’s chemistry remains an unknown secret, there is scope for optimism as research has suggested the existence of isotopes with a longer half-life. When scientists crack the ways to produce atoms of those isotopes, the chemical and physical properties of meitnerium will finally move out from the realm of educated speculation.


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Printable version | Oct 21, 2021 9:13:43 PM | https://www.thehindu.com/children/the-meitnerium-mystery/article36014472.ece

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