Technetium

In the late 1800s, Dmitri Mendeleev’s pioneering periodic table predicted the existence of element 43. That prediction led to something of a scientific treasure hunt, with many teams of researchers vying to be the first to find the element. After all, who wouldn’t want to be the first person to discover an element?

In 1925, a German team reported that they discovered element 43, naming it “masurium.” But because other scientists couldn’t replicate the researchers’ results, doubt remained about whether the element had really been discovered.

It wasn’t until 1937 that Italian scientists Carlo Perrier and Emilio Segrè officially discovered element 43. They did this using the discarded parts of a cyclotron—a kind of particle accelerator that is used to smash atoms into pieces. Segrè acquired the cyclotron parts from American physicist Ernest O. Lawrence (proving in the process that one person’s trash really is another person’s treasure). Because technetium was the first artificially produced element, Perrier and Segrè named the element after the Greek word teknet, meaning “artificial.”

Technetium is a silvery-grey metal that looks like platinum and tarnishes slowly in moist air. The element’s chemistry is a lot like that of rhenium, its neighbor in the periodic table.

Technetium can be mixed into steel to help prevent rusting. However, because technetium is radioactive, its applications in steel production are limited.

The most important technetium isotope is technetium-99, which is made in nuclear reactors when uranium-235 fissions, or splits apart. When technetium-99 breaks down, the isotope emits a gamma ray (an electromagnetic wave like an x-ray, but with a shorter wavelength). Doctors can inject technetium in a patient and, by monitoring the gamma rays, “see” how well certain organs are working. Technetium-99 is used in millions of medical procedures each year.

Technetium is the lowest-numbered element in the periodic table whose every isotope is radioactive. The longest-lived technetium isotope, technetium-97, has a half-life of some 4.2 million years. That might sound like a long time, but not compared to the age of the Earth!

Technetium’s relatively short half-life is why scientists had such a hard time discovering the element. Among the 30 other technetium isotopes that have been identified, almost all have half-lives of less than one hour.

Technetium can be produced in particle accelerators. However, most technetium comes about as a byproduct of nuclear fission reactions, when radioactive elements, like uranium, split apart. For this reason, although technetium’s name comes from the word for “artificial,” technetium occurs naturally among uranium ores.

Most commercially produced technetium comes from spent nuclear fuel rods. But technetium isn’t found just on Earth. By analyzing the light that comes from space, scientists have figured out that certain kinds of stars make technetium, too!