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Technetium (Tc)

Technetium is a chemical element of the periodic table with chemical symbol Tc and atomic number 43 with an atomic weight of 98.9062 u and is classed as transition metal and is part of group 7 (manganese group). Technetium is solid at room temperature.

Technetium in the periodic table

Atomic number43
Group7 (Manganese group)
ClassificationTransition Metal
AppearanceShiny gray metal
Color Silver
Number of protons43 p+
Number of neutrons55 n0
Number of electrons43 e-
From Wikipedia, the free encyclopediaTechnetium (/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.

Physical properties

Phase at STPSolid
Density11 g/cm3
Atomic weight98.9062 u

Thermal properties

Melting point2430 K
2156.85 °C
3914.33 °F
Boiling point4538 K
4264.85 °C
7708.73 °F
Heat of vaporization502 kJ/mol

Atomic properties

Electronegativity (Pauling Scale)1.9
Electron affinity53 kJ/mol
Oxidation states−3, −1, 0, +1, +2, +3, +4, +5, +6, +7
(a strongly acidic oxide)
Ionization energies
  1. 702 kJ/mol
  2. 1470 kJ/mol
  3. 2850 kJ/mol

Electron configuration for technetium

Electron configuration
Shorthand configuration
[Kr] 4d5 5s2
Electron configuration
Full configuration
1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d5 5s2
Electron configuration chart
Electrons per shell2, 8, 18, 13, 2
Valence electrons 7
Valency electrons 4
Bohr model
TechnetiumElectron shell for Technetium, created by Injosoft ABTc
Figure: Shell diagram of Technetium (Tc) atom.
Orbital Diagram

The history of Technetium

PredictionDmitri Mendeleev (1871)
Discovery and first isolationCarlo Perrier, Emilio Segrè (1937)
Discovery of technetium
From the 1860s through 1871, early forms of the periodic table proposed by Dmitri Mendeleev contained a gap between molybdenum (element 42) and ruthenium (element 44). In 1871, Mendeleev predicted this missing element would occupy the empty place below manganese and have similar chemical properties. The discovery of element 43 was finally confirmed in a 1937 experiment at the University of Palermo in Sicily by Carlo Perrier and Emilio Segrè. Segrè enlisted his colleague Perrier to attempt to prove, through comparative chemistry, that the molybdenum activity was indeed from an element with the atomic number 43. In 1937, they succeeded in isolating the isotopes technetium-95m and technetium-97. University of Palermo officials wanted them to name their discovery "panormium", after the Latin name for Palermo, Panormus. In 1947 element 43 was named after the Greek word τεχνητός, meaning "artificial", since it was the first element to be artificially produced.


List of unique identifiers for Technetium in various chemical registry databases
CAS Number7440-26-8
ChemSpider ID22396
EC number231-136-0
PubChem CID Number23957