ElementsWhat is technetium?
Technetium is a radioactive, silvery-grey metal. All its forms are unstable, so almost none exists naturally on Earth.
What is technetium used for?
A form called technetium-99m is the most widely used tracer in medical scans of bones, heart and other organs.
Where the name comes from
From the Greek word technetos, artificial. It was the first element to be made by people.
Key facts
- Symbol
- Tc
- Atomic number
- 43
- Atomic mass
- 96.90636 u
- Family
- Transition metal
- Period
- 5
- Group
- 7
- Block
- d
- State at room temperature
- Solid
- Melting point
- 2,157 °C (2,430 K, 3,914 °F)
- Boiling point
- 4,265 °C (4,538 K, 7,709 °F)
- Density
- 11 g/cm³
- Electrons per shell
- 2, 8, 18, 13, 2
- Electron configuration
- [Kr]5s2 4d5
- Common oxidation states
- +7, +6, +4
- Electronegativity (Pauling)
- 1.9
- First ionisation energy
- 7.28 eV
- Electron affinity
- 0.55 eV
- Atomic radius (van der Waals)
- 209 pm
- Discovered
- 1937
Place in the periodic table
Technetium is element number 43. It sits in period 5 (row 5) of the periodic table, in group 7 (column 7), and belongs to the d-block. Just before it comes molybdenum (42), and just after it comes ruthenium (44). In the same column, manganese is above it and rhenium is below it. Elements in one column tend to behave alike.
Family: Transition metals.
Physical properties
At room temperature technetium is a solid. It melts at 2,157 °C and boils at 4,265 °C, so it stays liquid over a range of 2,108 degrees. Its density is 11 grams per cubic centimetre, so a one-litre block would weigh about 11 kilograms. By density it ranks 23rd among the 96 elements with a measured value.
Inside the atom
An atom of technetium has 43 protons in its nucleus and, when neutral, 43 electrons around it. The electrons are arranged in 5 shells: 2, 8, 18, 13, 2. The outermost shell holds 2 electrons. Written in full, the electron configuration is [Kr]5s2 4d5.
Its electronegativity on the Pauling scale is 1.9. This number shows how strongly an atom pulls shared electrons towards itself: fluorine, the strongest, is 3.98. Removing one electron from an atom takes 7.28 electronvolts (about 702 kilojoules per mole). One mole of technetium weighs 96.90636 grams, so a single gram contains about 6.21 × 1021 atoms.
The ring picture is a simple model that only counts the electrons in each shell. Real atoms do not look like this.
Next steps
- Work out the weight of a compound that contains technetium with the molar mass calculator.
- Compare it with every other element in the sortable list.
- Test yourself with the symbol quiz.
Figures on this page are from PubChem (U.S. National Library of Medicine), as downloaded on 11 November 2026. See About and data sources.