Technetium (Tc)
Transition metal · Radioactive · Synthetic
Technetium was the first artificially made element — the gap at number 43 that Mendeleev had predicted was finally filled in a cyclotron in 1937. Today its metastable isotope Tc-99m is the workhorse of nuclear medicine imaging.
Position on the periodic table
Atomic properties
| Atomic number | 43 |
|---|---|
| Atomic mass | 98 amu |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d5 |
| Noble gas shorthand | [Kr] 4d5 5s2 |
| Electrons per shell | 2, 8, 18, 13, 2 |
| Valence electrons (outer shell) | 2 |
| Common oxidation states | +7, +4 |
| Electronegativity (Pauling) | 1.9 |
| Covalent radius (approx.) | 147 pm |
| First ionization energy | 702 kJ/mol |
| Electron affinity | 53 kJ/mol |
Physical properties
| State at 25 °C | Solid |
|---|---|
| Density | 11 g/cm³ |
| Melting point | 2156.8 °C (2430 K) |
| Boiling point | 4264.9 °C (4538 K) |
| Appearance | shiny gray metal |
| Radioactive | Yes |
| Origin | Synthetic (lab-made) |
Electron configuration of technetium
Technetium's ground-state electron configuration is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d5, usually shortened to [Kr] 4d5 5s2. Its electrons occupy 5 shells (2, 8, 18, 13, 2), placing it in period 5 of the d-block. Explore it interactively in the electron configuration calculator.
Uses of technetium
- Medical imaging (Tc-99m scans of heart, bones and organs)
- Research tracer
- Corrosion-inhibiting additive (specialist use)
Biological role: None — used only as a short-lived medical tracer.
Occurrence: Only trace amounts exist naturally from uranium fission; essentially all technetium is made in reactors.
Common compounds of technetium
TcO4
Pertechnetate ion (as salts)
History and discovery
Discovered: 1937 — Emilio Segrè. Name origin: From Greek technetos, meaning artificial.
Carlo Perrier and Emilio Segrè identified technetium in 1937 in molybdenum foil bombarded in a cyclotron.
Safety notes
All isotopes are radioactive; medical use involves tiny, carefully controlled doses.
Educational context only — always follow your school's laboratory rules and never handle chemicals without proper supervision. See our disclaimer.
Practice questions
Quick practice: Technetium
1. What is the chemical symbol of Technetium?
2. What is the atomic number of Technetium?
3. Which category does Technetium belong to?
4. What is the state of Technetium at room temperature?
5. Which period of the periodic table is Technetium in?
Technetium FAQs
What is the atomic number of technetium?
Technetium's atomic number is 43 — every technetium atom has 43 protons in its nucleus.
What is the symbol for technetium?
Tc. From Greek technetos, meaning artificial.
Is technetium a metal, nonmetal, or metalloid?
Technetium is classified as a transition metal.
What state is technetium at room temperature?
At about 25 °C, technetium is a solid. It melts at 2156.8 °C.
What is technetium used for?
Key uses include: medical imaging (tc-99m scans of heart, bones and organs); research tracer; corrosion-inhibiting additive (specialist use).
Related elements
Keep working with this element
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