Technetium

Technetium is a silvery-gray transition metal with no stable isotopes: every form of it is radioactive. Tiny amounts form naturally when uranium atoms split in ores, but these traces are too scarce to mine. Useful supplies are made through nuclear reactions in reactors or particle accelerators. For medical scans, technetium-99m is commonly collected from the decay of reactor-produced molybdenum-99. Compounds containing this short-lived form travel to particular tissues, where their gamma rays allow special cameras to image bones and organs. Its half-life is about six hours, so its activity falls quickly. Technetium has also been detected in red giant stars, providing evidence that stars make new elements within themselves.