Technetium

A chemical element, in the periodic table Technetium has the symbol Tc and atom number 43.

Technetium is unusual because it has no stable isotopes, and so none of it could be found anywhere on Earth, all Technetium of natural origin having decayed long ago. For a number of years, there was a gap in the periodic table corresponding to Technetium, until, with the development of nuclear energy in the 20th century, it could be generated by nuclear reactions. (hence its name, to mark its existence on Earth as the product of technology) Once it was available in macroscopic quantities i.e. enough to determine its chemical and physical properties, it was discovered to exist naturally elsewhere in the universe - some red giant stars contain an emission line in their spectrum corresponding to the presence of technetium.