Periodic TableTechnetium (Tc)
Technetium is a transition metal with atomic number 43, in period 5 and group 7 of the periodic table. Its atomic mass is 97 u and its electron configuration is [Kr] 4d⁵ 5s². Solid at 25 °C.
Key facts
| Atomic number | 43 |
|---|---|
| Atomic mass | 97 u |
| Category | Transition Metal |
| Period | 5 |
| Group | 7 |
| Block | d |
| Electron configuration | [Kr] 4d⁵ 5s² |
| Electrons per shell | 2, 8, 18, 13, 2 |
| Electronegativity (Pauling) | 1.9 |
| Oxidation states | −3, −1, +1, +2, +3, +4, +5, +6, +7common in bold |
| State at 25 °C | Solid |
| Melting point | 2430 K2156.85 °C |
| Boiling point | 4538 K4264.85 °C |
| Density | 11 g/cm³ |
Atomic properties
| First ionization energy | 7.28 eV |
|---|---|
| Electron affinity | 53 kJ/mol |
| Atomic radius | 136 pm |
| Covalent radius | 147 pm |
| Van der Waals radius | 209 pm |
| Common ions | Tc⁷⁺ |
| Protons, neutrons, electrons | 43, 54, 43 |
Physical and thermal properties
| Molar volume | 8.63 cm³/mol |
|---|---|
| Heat of fusion | 23 kJ/mol |
| Heat of vaporization | 550 kJ/mol |
| Specific heat | 63 J/(kg·K) |
| Thermal conductivity | 51 W/(m·K) |
| Thermal expansion | --- |
| Mohs hardness | --- |
| Young’s modulus | --- |
| Crystal structure | Simple hexagonal |
| Magnetic type | Paramagnetic |
Identification and history
| CAS number | 7440-26-8 |
|---|---|
| Latin name | Technetium |
| Discovered by | E. Segrè, C. Perrier · 1937 |
| Named by | --- |
Natural isotopes
Technetium has no stable isotopes: every isotope is radioactive.
Data checked against PubChem (NIH), IUPAC, the NIST Atomic Spectra Database and the IAEA (NUBASE and AME), the same data you see in the app.
A dash (---) means there is no reliable published measurement. The app never makes one up.
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