Technetium (Tc) is a silver-gray radioactive metallic element in group VIIB of the periodic table; a transition element. Technetium does not occur naturally on Earth. It was first made in 1937 by Emilio Segré and Carlo Perrier in bombarded molybdenum – the first element to be produced artificially. It is now recovered from the fission products of uranium in nuclear reactors and is used in radioactive tracer studies. Technetium is chemically very like rhenium. There are 16 known isotopes, the most stable of which is 99Tc (half-life 2.6 million years).


atomic number 43
relative atomic mass 99
relative density 11.5
melting point 2,140°C (3,884°F)
boiling point 5,030°C (9,086°F)