ELEMENTLE

Element 43 · Transition Metal

Technetium

Period 5 · Group 7

Technetium (/tɛkˈniːʃiəm/) is a chemical element with symbol Tc and atomic number 43. It is the element with the lowest atomic number in the periodic table that has no stable isotopes:every form of it is radioactive. Nearly all technetium is produced synthetically, and only minute amounts are found in nature.

Three reasons Technetium stands out

  1. 1

    Radioactive and used in medical imaging.

  2. 2

    It was the first element to be artificially created rather than discovered in nature, synthesised in 1937.

  3. 3

    It has no stable isotopes at all — every single form of it is radioactive.

The first element made by human hands

Technetium was the first element produced artificially, filling a conspicuous gap in the periodic table. Every isotope is radioactive, explaining its near absence from old terrestrial rocks. The short-lived metastable isotope technetium-99m became a workhorse of medical imaging because its gamma rays can be detected outside the body.

Technetium at a glance
Atomic number / protons43
SymbolTc
Family (Elementle)Transition Metal
Classification (PubChem)Transition metal
Period5
Group7
Atomic mass (u)96.90636
Standard stateSolid
Electron configuration[Kr]5s2 4d5
Reported oxidation states+7, +6, +4
Electronegativity (Pauling)1.9
Atomic radius (pm)209
First ionization energy (eV)7.28
Electron affinity (eV)0.55
Density (g/cm³)11
Melting point2430 K (2,156.85 °C)
Boiling point4538 K (4,264.85 °C)
Discovery (PubChem)1937

Values are reference data, not a specification for every temperature, pressure, or allotrope. Unknown properties are left unavailable. Superheavy-element predictions remain uncertain.

Sources & further reading

PubChem: Technetium · Technetium on Wikipedia

The introduction and original editorial story are adapted from Wikipedia contributors via Periodic-Table-JSON. Element descriptions and their adaptations are available under CC BY-SA 3.0. Numerical attributes use the PubChem periodic-table dataset, retrieved September 22, 2026.