Assertion: technetium's isotope | /r/HasProperty | known with mass numbers
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text: Technetium was the first man-made element, and was obtained as the isotopes 95Tc and 97Tc by Perrier and Segré in 1937 by bombarding molybdenum with deuterons.1,1a Today, 34 isotopes of element Tc are known with mass numbers ranging from 85 to 118, and all are radioactive.