Element Technetium, Tc, Transition Metal

As part of his famous predictions Dmitri Mendeleev showed that there is a missing element, would be chemically similar to manganese and gave it the name ekamanganese (chemical element number 43) with approximate atomic weight 100 as well as and dvi-manganese (chemical element number 75). By that year of 1871 it had been suggested that in 1846 this element called ilmenium had been discovered by R. Hermann in a sample of mineral yttroilmenite also known as samarskite. Even though Heinrich Rose later disproved this discovery, Mendeleev presumed that ilmenium might have turned out to be ekasilicon.

In 1925 German chemists Walter Noddack, and Ida Tacke reported the discovery of chemical elements number 43 and 75; the former was named masurium and the latter had been called rhenium. The existence of the latter had been confirmed completely, what was not supported for masurium.

In early 1937 Lawrence mailed Emilio Segre scrap of radioactive molybdenum that had been part of the deflector in the Berkeley 27" cyclotron. Segre enlisted his experienced chemist colleague Carlo Perrier to attempt to prove through comparative chemistry that the molybdenum, zirconium and niobium activity could be also related also with rhenium and magnesium and was indeed related with chemical element number 43, not existent in nature because of its instability against nuclear decay. Soon after that also 5 isotopes were isolated. Segre working with Chien-Shung Wu the research for part of the thesis he supervised of, again encountered element number 43 among fission products in 1940. After F.A. Paneth suggested in 1947 that the first producer of an artificial element be entitled to name the element, Segre and Perrier suggest the name technetium, after the Greek word technetos, meaning "artificial", since it was the first element to be artificially produced.

Since technetium is unstable, only minute traces occur naturally in the Earth's crust as UO_(2+x). Lines of technetium have been found in solar and other stars spectra.