Periodic Table


Atomic number: 43
Atomic weight: 98
Symbol: Tc
Group number: 7
Electronic configuration: [Kr].4d6.5s2


Since its discovery, searches for the element technetium in terrestrial materials have been made without success. Technetium has been found in the spectrum of S-, M-, and N-type stars, and its presence in stellar matter is leading to new theories of the production of heavy elements in the stars.

Technetium is a silvery-grey metal that tarnishes slowly in moist air. Until 1960, technetium was available only in small amounts. The chemistry of technetium is related to that of rhenium.

General information

Discoveror: Carlo Perrier, Emilio Segre
Date discovered: 1937
Discovered at: Italy
Meaning of name: From the Greek word "technikos" meaning "artificial"

Physical data

Standard state: solid at 298 K
Colour: silvery grey metallic
Density of solid at ambient temperature/kg m-3: 11500
Molar volume/cm3: 8.63

Radii /pm

Atomic: 183
Covalent (single bond):
Pauling radius for the ion [Tc]-: no data

Valence shell orbital radius maxima (Rmax)
orbital s p d f
radius157.4no data66.8no data


Both values are quoted on the Pauling scale.

Pauling: 1.9
Allred Rochow: 1.36

Crystal Structure

structure: hcp (hexagonal close-packed)

The following CrystalMaker image represents the solid state structure. For most elements, the most stable allotrope is illustrated. Try WebElements version 2 for interactive virtual reality and CHIME images.


Temperatures (/K)

melting point: 2430
boiling point: 4538

Enthalpies /kJ mol-1

fusion: 23.8
vaporization: 540

single bond enthalpies:
Tc-F Tc-Cl Tc-Br Tc-I Tc-Tc
no data no data no data no data no data

Ionization enthalpies /kJ mol-1

Number Enthalpy


This section gives some data for naturally occurring isotopes.
Nominal mass Accurate mass % natural abundance

Further Information

Copyright 1997 Mark Winter
Department of Chemistry at the University of Sheffield, Sheffield S3 7HF, England.

The current version of this document is at http://www.shef.ac.uk/~chem/web-elements-I/Tc.html