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.

Recognizing Technetium in Elementle

If Technetium is the mystery element, guesses below atomic number 43 point up and guesses above it point down. Its symbol is Tc: a green letter matches the same position in that symbol, while a yellow letter belongs in another position.

The family clue turns green for transition metal guesses. Compare Molybdenum (Mo), number 42 and Ruthenium (Ru), number 44: they share the family clue, but their atomic numbers and symbols help you tell them apart.

Learn how to read the clues or play the daily element guessing game.

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.