Technetium
Element 43 · Transition Metal
Technetium holds a special place in chemistry as the first element produced artificially: in 1937, Perrier and Segrè created it by bombarding molybdenum with deuterons, filling the mysterious gap at atomic number 43. Every isotope of technetium is radioactive, which is why the element went undiscovered in nature for so long. Its most famous isotope, technetium-99m, emits easily detected gamma rays and decays with a 6-hour half-life — ideal for medical imaging, where it is injected in tiny amounts to map blood flow, bones, and organs before quickly fading away.
Key facts
| Atomic number | 43 |
|---|---|
| Atomic weight | [98] |
| Category | Transition Metal |
| Group / Period | 7 / 5 |
| Block | d |
| Electron configuration | [Kr] 4d5 5s2 |
| Common oxidation states | +7, +4 |
| State at STP | Solid |
| Electronegativity | 1.9 |
| Atomic radius | 136 pm (empirical) |
| Density | 11 g/cm³ |
| Melting point | 2157 °C |
| Boiling point | 4265 °C |
Occurrence
Technetium occurs only in trace amounts in uranium ores as a spontaneous fission product. Virtually all technetium used today is produced artificially in nuclear reactors, where molybdenum-99 decays into technetium-99m.
Applications
Medical imaging (technetium-99m scans)
Industrial thickness and level gauges
Nuclear medicine research
Common compounds
- Sodium pertechnetate
- Technetium-99m labeled tracers
Technetium-99m is the workhorse of nuclear medicine, used in tens of millions of diagnostic scans each year — its short 6-hour half-life keeps patient radiation doses low.
Data source: IUPAC standard atomic weights 2021 (bracketed value is the mass number of the most stable isotope); NIST physical property data