From WordNet (r) 3.0 (2006) :
technetium
n 1: a crystalline metallic element not found in nature; occurs
as one of the fission products of uranium [syn:
technetium, Tc, atomic number 43]
From The Elements (07Nov00) :
technetium Symbol: Tc Atomic number: 43 Atomic weight: (98) Radioactive metallic transition element. Can be detected in some stars and the fission products of uranium. First made by Perrier and Segre by bombarding molybdenum with deutrons, giving them Tc-97. Tc-99 is the most stable isotope with a half-life of 2.6*10^6 years. Sixteen isotopes are known. Organic technetium compounds are used in bone imaging. Chemical properties are intermediate between rhenium and manganese.