- Technetium (Tc) is a transition metal with atomic number 43, located in Group 7 of the periodic table between manganese and rhenium.
- It is a silvery-gray, brittle metal that exhibits metallic properties but is radioactive, with no stable isotopes.
- Its most common isotope, technetium-98 (⁹⁸Tc), has a half-life of about 4.2 million years, while the isotope technetium-99 (⁹⁹Tc) has a half-life of 211,000 years and is widely encountered in nuclear medicine and fission products.
- Technetium has seven valence electrons—two in the 5s subshell and five in the 4d subshell—and typically exhibits oxidation states ranging from +7 to +4, with +7 being the most stable in compounds such as pertechnetate (TcO₄⁻). Its atomic structure consists of forty-three protons, a variable number of neutrons depending on the isotope, and forty-three electrons arranged in five shells.
- Technetium is extremely rare in the Earth’s crust because all naturally occurring isotopes are radioactive and decay over time. Trace amounts can be found in uranium ores due to spontaneous fission of uranium-238, but the element was first artificially produced in 1937 by Italian chemists Carlo Perrier and Emilio Segrè through the bombardment of molybdenum with deuterons. The name “technetium” derives from the Greek technetos, meaning “artificial,” reflecting its status as the first artificially produced element.
- The principal applications of technetium are in nuclear medicine, particularly the isotope technetium-99m (⁹⁹ᵐTc), a metastable form with a half-life of six hours. This isotope emits gamma radiation suitable for imaging internal organs and bone structures using single-photon emission computed tomography (SPECT). Approximately 80–85% of all nuclear medicine procedures use technetium-99m because it provides clear images while minimizing radiation exposure to the patient.
- Technetium also finds limited use in industrial applications, such as corrosion-resistant coatings and alloys. It can form intermetallic compounds with steel and nickel, improving their resistance to corrosion and high-temperature oxidation. However, these applications are limited due to its radioactivity and scarcity.
- Chemically, technetium behaves similarly to rhenium and manganese. It forms oxides, halides, and coordination complexes, with pertechnetate ion (TcO₄⁻) being highly soluble in water and chemically stable under oxidizing conditions. It also forms nitrides, sulfides, and various organometallic compounds. Its chemistry is dominated by the +7 oxidation state in aqueous solutions, though lower oxidation states are stable under reducing conditions.
- Biologically, technetium has no known essential role in organisms. However, technetium-99m is widely used safely in medical diagnostics due to its short half-life and emission of gamma rays rather than alpha or beta particles. Prolonged exposure to other isotopes can be hazardous due to radioactivity.
- From an environmental perspective, technetium-99 is considered a long-lived radioactive contaminant, primarily produced in nuclear reactors and fission of uranium and plutonium. Proper handling and disposal are critical to prevent contamination of water and soil.
