IT'S ELEMENTAL!
very similar to the direct measurements of natural technetium abundance in uranium ore published in 1999 by Dave Curtis and colleagues at Los Alamos. We can find no other plausible explanation for the JOHN T. ARMSTRONG, NATIONAL INSTITUTE OF STANDARDS & TECHNOLOGY Noddacks' data than that they did indeed F YOU READ ABOUT TECHNETIUM I N named "masurium") in samples from ura- detect fission "masurium." The Noddacks were clearly among the the "Handbook of Chemistry and nium-rich ores. Physics," you might think you knew Van Assche speculated that, although finest analytical geochemists of their time. all you needed to about its discovery the researchers didn't realize it, Their search for the "missing" eland existence. That's how I felt the they had isolated terrestrial ements below manganese in the first time I had to deal with this rare ele- technetium-9 9 formed from periodic table was part of a largment. But simple stories can be deceptive. the spontaneous fission of uraer effort to accurately determine I first encountered technetium short- nium. I was skeptical, but after the abundance of the chemical ly after I got my Ph.D. While doing a stint studying their paper, I realized elements in the earth and meteas a researcher in an industrial micro- that they were clearly not crackorites—data that provided a analysis laboratory, I was asked to deter- pots or, as Ernest Lawrence foundation for the science ofgeomine the distribution of technetium on called them, "apparently deludchemistry Their work compleCELEBRATING: : bone surfaces using electron microscopy ed." In the same article, the auG&EN'S mented rather than detracted 80TH and X-ray analysis. It was the first time I thors claimed discovery of elefrom that of Perrier and Segre. ANNIVERSARY measured X-ray spectra of technetium, ment 75, naming it "rhenium." I am pleased to see that Ida and Ifiguredit might well be the last. The Both claims were widely disNoddack-Tacke's contributions technetium-9 9 in the radiopharmaceuti- puted at the time, but three years later, to science are being rediscovered—on the cal was made by neutron irradiation of the Noddacks isolated weighable amounts Web and in recent books about the perimolybdenum, similar to the technetium of rhenium and were accepted as its dis- odic table. As a participant in this scienfirst analyzed by Carlo Perrier and Emilio coverers. They weren't able to so concen- tific detective adventure, I'll always have Segre in 1937. Since the longest lived iso- trate masurium, and the International a fondness for the "element that was distope of technetium has a half-life of about Union of Pure & Applied Chemistry even- covered twice"—first as masurium, the 4 million years, the conventional wisdom tually rejected that discovery The conwas that no detectable natural technetium troversy clearly affected their reputations. TECHNETIUM AT A GLANCE could be found on Earth. Little attention was paid to Ida NodName: From the Greek technetos, Certainly, I didn't find any during the dack-Tacke's article in 1935 questioning next 20 years. I moved on from industry Enrico Fermi's claim that he discovered artificial. and spent 15 years in the Atomic mass: 198). v the transuranium element Geological & Planetary History: Discovered in 1937 by Carlo 1 93 (for which he received the Sciences Division at CaliPerrier and Emilio Segre. It is the first =• Nobel Prize) and suggesting fornia Institute of Techartificially produced element. Since its 0 that his neutron bombardnology, using electron and discovery, searches for technetium in i ment of uranium may have ion microprobe analysis to terrestrial materials have been made 2 resulted in the atoms disinstudy the oldest phases in without success until recently. Tech•J tegrating into fragments. It meteorites. Technetium is netium has been found in the spectrum | was not until Lise Meitner found in the spectra of of S-, M-, and N-type stars, and its £ and colleagues' "discovery" stars and has interesting presence in stellar matter is leading to 2 of nuclear fission in 1939 implications for nucleonew theories of the production of heavy t that she was proved right. synthesis. If it had stable elements in the stars. 1 After this time, the Nodisotopes, I would likely Occurrence: Artificially produced. < dacks led lives of relative scio have studied it. But since Appearance: Silvery gray metal. SS entific obscurity it didn't, I doubt that I Ida Noddack-Tacke Behavior: Radioactive. Tarnishes slow< Using first-principles Xspent as much as an hour ly in moist air. ray-emission spectral-genthinking about its occurrence. Uses: Used as a medical tracer and to eration algorithms developed at NIST, I It wasn't until 1998 that I took a real calibrate particle detectors. look at element 43.1 was now at the Na- simulated the X-ray spectra that would be tional Institute of Standards & Technol- expected for Van Assche's initial estimates first natural element discovered composed ogy (NIST), in the Surface & Micro- of the Noddacks' residue compositions. entirely of a spontaneousfissionproduct; analysis Science Division. One day, an The first results were surprisingly close to second as technetium, the first man-made exuberant Belgian physicist, Pieter van their published spectrum! Over the next chemical element. Assche, came into my office to ask my in- couple of years, we refined our reconterpretation of an X-ray emission spec- struction of their analytical methods and John T. Armstrong is a research chemist at trum. The spectrum was from a 1925 ar- performed more sophisticated simula- NIST, Gaithersburg, Md. He does fundamenticle by Ida Noddack-Tacke, Walter tions. The agreement between simulated tal and applied research on electron and X-ray Noddack, and Otto Berg, who claimed to and reported spectra improved further. spectrometry and is a past president of the Microbeam Analysis Society. have discovered element 43 (which they Our calculation of the amount of element 43 required to produce their spectrum is
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