 Discovery Information
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| Who: Carlo Perrier, Emillo Segre |
| When: 1937 |
| Where: Italy |
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| Name Origin
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| Greek: technetos (artificial). |
| "Technetium" in different languages. |
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| Sources
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| Made first by bombarding molybdenum with deuterons (heavy hydrogen) in a cyclotron.
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| Uses
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| The technetium-99m isotope serves as a radiation source in medicine where it is used to locate tumours in the spleen, liver, brain, and thyroid. When 99mTc is combined with a tin compound it binds to red blood cells and can therefore be used to map circulatory system disorders. Technetium-99 is used
for equipment calibration.
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| History
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| For a number of years there was a gap in the periodic table between molybdenum (element 42) and ruthenium (element 44). Many early researchers were eager to be the first to discover and name the missing element; its location in
the table suggested that it should be easier to find than other undiscovered elements. It was first thought to have been found
in platinum ores in 1828. It was given the name polinium but it turned out to be impure iridium. Then in 1846 the element
ilmenium was claimed to have been discovered but was determined to be impure niobium. This mistake was repeated in 1847 with
the "discovery" of pelopium. Dmitri Mendeleev predicted that this missing element, as part of other predictions, would be
chemically similar to manganese and gave it the name ekamanganese.
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| In 1877, the Russian chemist Serge Kern reported discovering the missing element in platinum ore. Kern named what he thought was the new element "davyum", after the noted English chemist Sir Humphry Davy, but it was determined to be a mixture of iridium, rhodium and iron. Another candidate, lucium, followed in 1896 but it was determined to be yttrium. Then in 1908 the Japanese chemist Masataka Ogawa found evidence in the mineral thorianite (ThO2) which he thought indicated the presence of element 43. Ogawa named the element nipponium, after Japan (which is Nippon in
Japanese). In 2004 H. K YOSHIHARA utilized "a record of X-ray spectrum of Ogawa's nipponium sample from thorianite [which]
was contained in a photographic plate reserved by his family. The spectrum was read and indicated the absence of the element
43 and the presence of the element 75 (rhenium)."
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| German chemists Walter Noddack, Otto Berg and Ida Tacke (later Mrs. Noddack) reported the discovery of element 75 and element 43 in 1925 and named element 43 masurium (after Masuria
in eastern Prussia, now in Poland, the region where Walter Noddack's family originated). The group bombarded columbite with
a beam of electrons and deduced element 43 was present by examining X-ray diffraction spectrograms. The wavelength of the
X-rays produced is related to the atomic number by a formula derived by Henry Moseley in 1913. The team claimed to detect
a faint X-ray signal at a wavelength produced by element 43. Contemporary experimenters could not replicate the discovery,
and in fact it was dismissed as an error for many years.
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| Discovery of element 43 was finally confirmed in a 1937 experiment at the University of Palermo in Sicily conducted by Carlo
Perrier and Emilio Segre. In the summer of 1936 Segre and his wife visited the United States, first New York at Columbia University, where he had spent time the previous summer, and then Berkeley at Lawrence's Radiation
Laboratory. He persuaded cyclotron inventor Ernest Lawrence to let him take back some discarded cyclotron parts that had become
radioactive. In early 1937 Lawrence mailed him a molybdenum foil that had been part of the deflector in the cyclotron. Segre enlisted his experienced chemist colleague Carlo Perrier
to attempt to prove through comparative chemistry that the molybdenum activity was indeed Z = 43, an element not existent
in nature because of its instability against nuclear decay. With considerable difficulty they finally succeeded in isolating
three distinct decay periods (90, 80, and 50 days) that eventually turned out to be two isotopes, 95Tc and 97Tc, of technetium,
the name given later by Perrier and Segre to the first man-made element. University of Palermo officials wanted them to name
their discovery panormium, after the Latin name for Palermo, Panormus. The researchers instead named element 43 after the
Greek word technetos, meaning "artificial", since it was the first element to be artificially produced. Segre returned to
Berkeley and immediately sought out Glenn T Seaborg. They isolated the technetium-99m isotope which is now used in some 10,000,000
medical diagnostic procedures annually.
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| In 1952 astronomer Paul W. Merrill in California detected the spectral signature of technetium (in particular, light at 403.1
nm, 423.8 nm, 426.8 nm, and 429.7 nm) in light from S-type red giants. These massive stars near the end of their lives were
rich in this short-lived element, meaning nuclear reactions within the stars must be producing it. This evidence was used
to bolster the then unproven theory that stars are where nucleosynthesis of the heavier elements occurs. More recently, such
observations provided evidence that elements were being formed by neutron capture in the s-process.
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| Notes
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| First artificially created element.
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| All isotopes of technetium are radioactive but the element and its compounds are extremely rarely found in nature.
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| Most technetium produced on Earth is a by-product of fission of uranium-235 in nuclear reactors and is extracted from nuclear fuel rods. On earth, technetium occurs naturally only in uranium ores as a product of spontaneous fission; the quantities are minute but have been measured.
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| No isotope of technetium has a half-life longer than 4.2 million years (98Tc), so its detection in red giants in 1952 helped bolster the theory that stars can produce heavier elements.
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