Technetium: the first artificial element that saved millions of lives

In Dmitrii Ivanovich Mendeleev's periodic table, there is a cell numbered 43. For many years, it remained empty. Its inhabitant did not give himself to chemists of the 19th century, hiding from the most persistent hunters for elements. But it turned out that it was not the complexity of separation, but the very nature of this substance: it simply could not survive on Earth since its formation. Today we know this element as technetium — the first element created artificially, and at the same time an element that saves thousands of lives every day in hospitals around the world.

Technetium is the only element lighter than lead that does not have stable isotopes. Its place in the table is a triumph of the predictive power of science and a monument to human ingenuity.

43rd element: Mendeleev's prophecy

In 1869, when Dmitrii Ivanovich Mendeleev presented his periodic table to the world, there were 63 elements and several empty spaces in it. He did not just leave gaps — he boldly predicted the properties of yet undiscovered substances. For the element numbered 43, which was located under manganese in the seventh group, the scientist predicted properties, calling it "eka-manganese" (from Sanskrit "eka" — one).

In the following decades, chemists searched for the missing element in manganese ores, minerals, and complex residues of chemical production. There were also loud declarations of discovery: the element was called "ilmium," "nioppium," "lurium." However, none of them was confirmed. Today we know why: technetium is radioactive, and its longest-lived isotopes with a half-life of about 4 million years have long disappeared from the Earth's crust since its formation.

Why "technetium"? The artificial origin of the name

The element received its name from the Greek word "τεχνητός" (technetos), which means "artificial." The name was prophetic in double: technetium became the first chemical element obtained artificially, not extracted from natural raw materials.

History of discovery: molybdenum foil from Berkeley

In 1937, Italian physicist Emilio Segrè worked in the United States, in the laboratory of Ernest Lawrence — the inventor of the cyclotron. Segrè noticed the strange radioactivity of one of the spent parts of the accelerator — molybdenum foil, which served as a target for deuterons.

The scientist assumed that a new element with number 43 was formed in molybdenum (atomic number 42) as a result of nuclear reactions. He took the foil with him to Palermo, where, together with mineralogist Carlo Perrier, he carried out a series of complex chemical operations. They managed to isolate the new radioactive element in pure, albeit microscopic, quantities.

Fundamental characteristic: the lightest without stable isotopes

Technetium is the lightest element in the periodic table that does not have any stable isotopes. Its "long-lived" forms are: Tc-97 (half-life of 2.6 million years), Tc-98 (4.2 million years), and the most accessible isotope — Tc-99 (half-life of 211,000 years).

At the same time, natural technetium does exist on Earth. In negligible, trace amounts (about 1 nanogram per ton of uranium ore), it is formed in the process of spontaneous fission of uranium-235. At any moment, there are about 18,000 tons of technetium in the Earth's crust — but this metal "dissolved" in vast volumes of rock formations.