Periodic Table of Elements




Technetium's existence was first predicted by Dmitri Mendeleev. Technetium was officially discovered by Carlo Perrier and Emilio Segrč in 1936 in an experiment at the University of Palermo in Sicily.

Name: Technetium
Symbol: Tc
Atomic number: 43
Atomic weight: 97.91
State: solid
Group, period, block: 7, 5, d
Color: shiny gray metal
Classification: transition metal
Electron configuration: 4d5 5s2

Physical properties

Density: 11 g/cm-3
Melting point: 2430 K,2157 °C,3915 °F
Boiling point: 4538 K,4265 °C,7709 °F

Atomic properties

Oxidation states: 7, 6, 5, 4, 3[1], 2, 1[2], -1, -3
Electronegativity: 1.9 (Pauling scale)
Ionization energies: 1st: 702 kJ·mol-1
Covalent radius: 147±7 pm
Van der Waals radius: no data
  • Tc
  • Electron Configuration


All isotopes of technetium are radioactive. The most stable radioactive isotopes are 98Tc with a half-life of 4.2 million years (Ma), 97Tc (half-life: 2.6 Ma) and 99Tc (half-life: 211,000 years).