Technetium is the chemical element with symbol Tc and atomic number 43. It is a radioactive transition metal and was the first element to be produced artificially before being identified in nature. All technetium isotopes are radioactive.
Technetium quick facts
| Property | Value |
| Symbol | Tc |
| Atomic number | 43 |
| Relative atomic mass | [98] |
| Group | 7 |
| Period | 5 |
| Block | d-block |
| State at 20°C | Solid |
| Density | About 11 g/cm³ |
| Melting point | 2157°C |
| Boiling point | 4262°C |
| Electron configuration | [Kr] 4d⁵ 5s² |
| Common oxidation states | +4, +7 |
| CAS number | 7440-26-8 |
| Important isotopes | ⁹⁹ᵐTc, ⁹⁹Tc |
Why technetium has no stable isotopes
Technetium sits between molybdenum and ruthenium, but unlike its neighbours it has no stable nuclide. Primordial technetium that may have existed when Earth formed has decayed away. Tiny amounts are continually produced naturally by spontaneous fission of uranium and by neutron-related nuclear processes, while much larger quantities are produced in nuclear reactors.
See the complete CleverlySmart periodic table.
Chemical properties and compounds
Technetium is a silvery metal whose chemistry resembles rhenium and, to a degree, manganese. One of its most important species is the pertechnetate ion, TcO₄⁻, in which technetium is in the +7 oxidation state. Pertechnetate chemistry is central to many radiopharmaceutical preparations.
- Pertechnetate (TcO₄⁻): a stable aqueous form used as a starting point for many Tc-99m radiopharmaceuticals.
- Technetium dioxide (TcO₂): a lower-oxidation-state oxide important in nuclear-waste chemistry.
- Technetium complexes: coordination compounds can be designed to target specific organs and physiological processes in medical imaging.
Technetium-99m in nuclear medicine
Technetium-99m (⁹⁹ᵐTc) is one of the most widely used radioisotopes in diagnostic nuclear medicine. It emits gamma radiation suitable for imaging and has a short physical half-life of about six hours, allowing useful scans while limiting long-term radiation exposure.
Different Tc-99m compounds accumulate in different tissues, allowing clinicians to image bones, the heart, kidneys, liver, lungs and other organs. Tc-99m is commonly supplied from molybdenum-99/technetium-99m generators.
Technetium-99 and other uses
Technetium-99 is a long-lived beta emitter and an important fission product in nuclear-waste management. Very small technetium additions can inhibit corrosion of steel in closed systems, but radioactivity prevents widespread use for ordinary corrosion protection.
Technetium isotopes
All known technetium isotopes are radioactive. The medically important metastable isotope ⁹⁹ᵐTc decays to ⁹⁹Tc. Other relatively long-lived isotopes include technetium-97 and technetium-98.
For isotope half-lives and decay pathways, see the CleverlySmart complete isotope table.
Biological role and radiation safety
Technetium has no known biological role. Its principal hazard is radioactivity. Medical technetium is used in carefully measured activities and under radiation-protection protocols. Long-lived Tc-99 is environmentally important because mobile pertechnetate can migrate through water under some conditions.
Discovery and name
Element 43 was long missing from the periodic table. In 1937, Carlo Perrier and Emilio Segrè identified it in molybdenum that had been bombarded in a cyclotron. The name comes from the Greek technetos, meaning artificial, reflecting its first confirmed production.
Frequently asked questions
Why is technetium-99m so useful for scans?
It has suitable gamma emission, a short half-life and chemistry that can be attached to compounds targeting many organs.
Does technetium occur naturally?
Yes, but only in tiny transient amounts produced by nuclear processes such as uranium fission. Commercial quantities are produced artificially.
Technetium-99m in medical imaging
The most important isotope in medicine is technetium-99m (⁹⁹ᵐTc), a short-lived metastable nuclear state that emits gamma radiation suitable for imaging. It is used in many diagnostic procedures because its roughly six-hour half-life is long enough for preparation and scanning but short enough to limit prolonged radiation exposure.
Hospitals commonly obtain ⁹⁹ᵐTc from molybdenum-99/technetium-99m generators. Different technetium-labelled compounds are designed to accumulate in particular organs or tissues, enabling functional imaging rather than only anatomical imaging.
Technetium-99 and nuclear waste
Technetium-99 has a much longer half-life and is produced in nuclear fission. Its pertechnetate ion, TcO₄⁻, can be mobile in oxygen-rich groundwater, making technetium chemistry relevant to long-term radioactive-waste management.
Frequently asked questions
Why is technetium called the first artificial element?
It was the first element to be produced and identified artificially before a substantial natural source was known.
Is technetium found in nature?
Yes, but only in extremely small transient amounts from processes such as spontaneous fission and neutron capture in uranium ores.
