Symbol	Tc
Atomic number	43
Group	7 (Manganese group)
Period	5
Block	d
Classification	Transition Metal

Appearance	Shiny gray metal
Color	Silver

Number of protons	43 p+
Number of neutrons	55 n0
Number of electrons	43 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.

Phase at STP	Solid
Density	11 g/cm3
Atomic weight	98.9062 u

Melting point	2430 K 2156.85 °C 3914.33 °F
Boiling point	4538 K 4264.85 °C 7708.73 °F
Heat of vaporization	502 kJ/mol

Electronegativity (Pauling Scale)	1.9
Electron affinity	53 kJ/mol
Oxidation states	−3, −1, 0, +1, +2, +3, +4, +5, +6, +7 (a strongly acidic oxide)
Ionization energies	702 kJ/mol 1470 kJ/mol 2850 kJ/mol

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

Prediction	Dmitri Mendeleev (1871)
Discovery and first isolation	Carlo 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.

CAS Number	7440-26-8
ChemSpider ID	22396
EC number	231-136-0
PubChem CID Number	23957