Technetium
Technetium (/tɛkˈniːʃiəm/) is a chemical element with symbol Tc and atomic number 43. It is the element with the lowest atomic number in the periodic table that has no stable isotopes:every form of it is radioactive. Nearly all technetium is produced synthetically, and only minute amounts are found in nature.
Identity
- Atomic mass
- [97] u
- Category
- Transition metals
- Group
- 7
- Period
- 5
- Block
- d
- Oxidation States
- +4, +7
- Phase (25 °C)
- Solid
- Appearance
- shiny gray metal
Electronic Structure
- Electron configuration
- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d5
- Short configuration
- [Kr] 4d5 5s2
- Electrons per shell
- 2, 8, 18, 13, 2
- Electronegativity (Pauling)
- 1.90
- Electron affinity
- 53 kJ/mol
- 1st ionization energy
- 702 kJ/mol
- Ionization energies
- 702 · 1470 · 2850 kJ/mol
Physical properties
- Melting point
- 2156.8 °C (2430 K)
- Boiling point
- 4264.9 °C (4538 K)
- Density
- 11 g/cm³
- Molar heat capacity
- 24.3 J/(mol·K)
Chemical behavior of technetium
Technetium is a group 7 transition metal with symbol Tc and atomic number 43. It is a silvery-gray metal, the first element produced artificially. All its isotopes are radioactive. Its states range from +4 to +7, with +7 (pertechnetate) the most stable in oxidizing media. Its name comes from Greek technetos (artificial).
Reactivity
Tc + 3 Cl2 -> TcCl4
Technetium reacts with chlorine to form technetium tetrachloride, a bluish-gray solid that is one of its most important compounds.
Tc + 2 H2SO4 -> Tc(SO4)2 + H2
Technetium reacts with hot concentrated sulfuric acid, releasing hydrogen and forming technetium sulfate.
Notable compounds
| Compound | Formula | Use or importance |
|---|---|---|
| Technetium(V) peroxotungstate | Tc2O7 | Orange solid; getter precursor and oxidant |
| Technetium hexafluoride | TcFs6 | Yellow solid; getter precursor and used in purification procedures |
| Technetium dichloride | TcCl4 | Bluish-gray solid; getter precursor and surface components |
Electron shell distribution
View in the atom builderIsotopes
Technetium has no stable isotopes. The longest-lived is technetium-97 (4.2-million-year half-life). Technetium-99 (211,000 years) is the main fission by-product. Technetium-99m, a metastable state, has a 6-hour half-life and is the workhorse of diagnostic imaging.
Occurrence and production
Essentially absent in nature; traces of technetium-99 arise in uranium ores by spontaneous fission. Virtually all supply comes from nuclear reactors as fission product, separated during fuel reprocessing, or from molybdenum-99 decay in generators.
History and origin of the name
Carlo Perrier and Emilio Segre identified it in 1937 in molybdenum bombarded with deuterons at Berkeley. They named it technetium for being the first element made artificially. Later production of Tc-97 and Tc-99 confirmed the discovery and opened nuclear medicine.
Applications and relevance of technetium
Uses of the element
Nearly all use is technetium-99m medical imaging: tens of millions of scans yearly for heart, bone, kidney and organ studies. Research uses tracers to follow chemical and biological processes in specialized labs.
Uses of its compounds
Pertechnetate eluted from Mo-99/Tc-99m generators is kit-built into radiopharmaceuticals (sestamibi, MDP, DTPA). Fluoride and chloride serve fluorine chemistry and precursor synthesis.
Health, safety and environment
Biological role
Technetium is not essential. Medical Tc-99m doses are small, short-lived and mainly excreted in urine; the gamma energy suits imaging while activity fades after the scan. Safety holds only at controlled clinical doses with supervision.
Safety
All isotopes need radiological control: shielding, containment, waste routing. Tc-99 has a very long half-life and must not disperse. Labs handling it need licensed facilities and procedures.
Environment
Environmental technetium is anthropogenic from reactors, reprocessing and fallout. Pertechnetate is mobile in water, so releases are strictly limited and monitored; generators and hospitals return waste to controlled circuits.
Frequently asked questions about Technetium
Why is technetium-99m the star of medical imaging?
One element feeds millions of scans: its 140 keV gamma rays escape the body for standard cameras, its 6-hour half-life limits patient dose, and generator supply fits hospitals. Kits bind it to molecules targeting heart, bone or kidneys.
What diseases can Tc-99m tests study?
Depending on the carrier molecule: heart blood flow, bone metabolism, kidney function and selected organs. Tc-99m maps distribution; diagnosis joins images with symptoms, history and other tests.
What is the difference between Tc-99m and Tc-99?
Same protons and neutrons, different nuclear energy: Tc-99m is the metastable excited state decaying by gamma emission in ~6 hours; Tc-99 is the ground state lasting ~211,000 years. Hence diagnostic use versus long-lived waste.
Why is steady Tc-99m supply hard to keep?
Six-hour half-life forbids stockpiling; hospitals rely on Mo-99 production, processing and fast transport. Research-reactor outages or logistics breaks cut availability, driving alternative production methods.
How does a Mo-99/Tc-99m generator work?
Molybdenum-99 fixed on a column decays to Tc-99m. Saline washed through elutes sodium pertechnetate while Mo-99 stays behind. This gives fresh short-lived doses on site without moving each dose from a distant plant.
Why is Tc-99m radiation suitable for imaging?
Mainly ~140 keV gamma photons detectable by conventional cameras. They exit the body to build distribution images, and short half-life lets activity decay after the exam. Choice balances nuclear and clinical practicality.
Can technetium trace scientific processes?
Yes. Its isotopes follow distribution and transformation in experiments: radiopharmaceuticals map physiology, complexes probe coordination chemistry. Isotope, chemical form and detector set the use; radioactivity needs licensed setups.
Main sources consulted: PubChem, Royal Society of Chemistry, NIST, IUPAC. Last revision: November 2026.