Technetium
transition metalProperties
| Property | Value |
|---|---|
| Atomic Mass | 97 amu |
| Category | transition metal |
| Group | 7 |
| Period | 5 |
| Electron Configuration | 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d5 |
| Electronegativity | 1.9 (Pauling) |
| Oxidation States | 7, 4, 2 |
| Melting Point | 2430 K (2156.8 °C) |
| Boiling Point | 4538 K (4264.9 °C) |
| Density | 11 g/cm³ |
| Discovered By | Carlo Perrier, Emilio Segre (1937) |
About Technetium
Technetium is the empty seat at the periodic table that Mendeleev predicted, Moseley's X-ray work confirmed was missing, and Perrier and Segrè finally filled in 1937 from a strip of cyclotron-bombarded molybdenum foil that Lawrence had mailed to Palermo. It has no stable isotopes — every nuclide it forms eventually decays — which is why Earth's primordial supply is gone and you have to make it. The workhorse isotope is Tc-99m, the metastable γ-emitter that sits at the center of nuclear medicine: a ⁹⁹Mo/⁹⁹ᵐTc generator at the hospital lets a technologist elute fresh Tc on demand, label it onto MDP for bone scans or sestamibi for cardiac perfusion, and inject it the same morning. Its 6-hour half-life and 140 keV photon are almost ideal — long enough to image, short enough that the patient is essentially clean by the next day.
Fun Fact
Tc-99m goes into about 40 million medical scans a year — and every dose was molybdenum a few hours earlier. The hospital's generator is a small column of acidic alumina holding ⁹⁹Mo; saline pulled through it elutes the daughter Tc as pertechnetate. Run the elution dry, wait a day, repeat.
Common Uses
- ⁹⁹ᵐTc-MDP injections for whole-body bone scintigraphy
- ⁹⁹ᵐTc-sestamibi and tetrofosmin for myocardial perfusion SPECT
- ⁹⁹ᵐTc-MAG3 and DTPA for renal function and clearance studies
- Sentinel-lymph-node mapping with ⁹⁹ᵐTc-sulfur colloid in breast and melanoma surgery
- Pertechnetate (TcO₄⁻) corrosion inhibitor in sealed reactor cooling loops
- Reference standard for calibrating SPECT and gamma cameras