Technetium

Technetium - Tc

CAS: 7440-26-8
Description: Radioactive, silvery-gray, man-made metal
Classification: Transition Metal
Date of Discovery: 1937
Discoverer: Carlo Perrier
Name Origin: Greek technêtos, "artificial"

Atomic Number: 43
Number of Neutrons: 55
Atomic Mass: (98) amu
Melting Point: 2157 °C
Boiling Point: 4265 °C
Density (293 K): 11.5 g/cm³ (calc.)
Atomic volume: 8.51 cm³/mol
Electrical resistivity:
Thermal conductivity: 50.6 J/m-sec-deg
Enthalpy of atomization: 649 kJ/mol (est.)
Enthalpy of vaporization: 660.0 kJ/mol
Enthalpy of fusion: 24.0 kJ/mol
Specific heat capacity: 0.21 J/gK

Energy levels: 2-8-18-14-1
Electron configuration: [Kr]4d⁵5s²
Crystal Structure: Hexagonal
Atomic radius: 1.27 Å
Covalent radius: 1.17 Å
Oxidation States: 0, +2, +4, +5, +6, and +7
Electronegativity, Pauling: 1.9
Electron affinity: 0.55 eV
First ionization energy: 702.4 kJ/mol
2nd ionization energy: 1472.4 kJ/mol
3rd ionization energy: 2850.2 kJ/mol
Polarizability: 11.4 10^-24cm³

Isotope	Natural Abundance	Atomic Mass	Half-life	Decay Mode	Spin
⁸⁶Tc	85.9430	⁺
⁸⁷Tc	86.9365	⁺
⁸⁸Tc	87.9328	⁺
^89mTc	13 s
⁸⁹Tc	88.9275	13 s	⁺
^90mTc	49.2 s	⁺	6+
⁹⁰Tc	89.9235	8.3 s	⁺	1+
^91mTc	3.3 m	⁺; EC
⁹¹Tc	90.9184	3.14 m	⁺	9/2+
⁹²Tc	91.91526	4.4 m	⁺; EC	8+
⁹³Tc	92.910248	2.73 h	⁺; EC	9/2+
^94mTc	52 m	⁺; EC	2+
⁹⁴Tc	93.909655	4.88 h	⁺; EC	7+
^95mTc	61 d	IT; ⁺; EC	1/2-
⁹⁵Tc	94.90766	20.0 h	EC	9/2+
^96mTc	52 m	IT; ⁺	4+
⁹⁶Tc	95.90787	4.3 d	EC	7+
^97mTc	90 d	IT	1/2-
⁹⁷Tc	96.906364	2.6 x 10⁶ y	EC	9/2+
⁹⁸Tc	97.907215	4.2 x 10⁶ y	^-	6+
^99mTc	6.01 h	IT	1/2-
⁹⁹Tc	98.906254	2.13 x 10⁵ y	^-	9/2+
¹⁰⁰Tc	99.907657	15.8 s	^-; EC	1+
¹⁰¹Tc	100.90731	14.2 m	^-	9/2+
^102mTc	4.4 m	IT
¹⁰²Tc	101.90921	5.3 s	^-	1+
¹⁰³Tc	102.90918	54 s	^-	5/2+
¹⁰⁴Tc	103.91144	18.2 m	^-	(3+)
¹⁰⁵Tc	104.91166	7.6 m	^-	5/2+
¹⁰⁶Tc	105.91436	36 s	^-	2+
¹⁰⁷Tc	106.9151	21.2 s	^-
¹⁰⁸Tc	107.9185	5.1 s	^-	(3)
¹⁰⁹Tc	108.9200	1.4 s	^-
¹¹⁰Tc	109.9234	0.83 s	^-
¹¹¹Tc	110.9251	0.30 s	^-
¹¹³Tc	112.931	0.13 s	^-
Element 43 was predicted on the basis of the periodic table, and was erroneously reported as having been discovered in 1925 at which time it was named masurium. The element was actually discovered by Perrier and Segre in Italy in 1937. It was found in a sample of molybdenum, which was bombarded by deuterons in the Berkeley cyclotron, and which E. Lawrence sent to these investigators. Technetium was the first element to be produced artificially. Since its discovery, searches for the element in terrestrial materials have been made without success. If it does exist, the concentration must be very small. 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. Thirty-one isotopes and isomers of technetium, with atomic masses ranging from 86 to 113 are known. ⁹⁷Tc has a half-life of 2.6 x 10⁶ years. ⁹⁸Tc has a half-life of 4.2 x 10⁶ years. The isomeric isotope ^95mTc, with a half-life of 61 days, is useful for tracer work, as it produces energetic gamma rays. Technetium metal has been produced in kilogram quantities. The metal was first prepared by passing hydrogen gas at 1100 °C over Tc₂S₂. It is now conveniently prepared by the reduction of ammonium pertechnetate with hydrogen. Technetium is a silver-gray metal that tarnishes slowly in moist air. The chemistry of technetium is said to be similar to that of rhenium. Technetium dissolves in nitric acid, aqua regia, and concentrated sulfuric acid, but is not soluble in hydrochloric acid of any strength. The element is a remarkable corrosion inhibitor for steel. It is reported that mild carbon steels may be effectively protected by as little as 55 ppm of KTcO₄ in aerated distilled water at temperatures up to 250 °C. This corrosion protection is limited to closed systems, since technetium is radioactive and must be confined. ⁹⁹Tc has a specific activity of 6.2 x 10⁸ Bq/g. Activity of this level must not be allowed to spread. ⁹⁹Tc is a contamimation hazard and should be handled in a glove box. The metal is an excellent superconductor at 11 K and below. LINKS: The Chemistry of Technetium Nitrido Complexes Determination of Technetium-99 in marine biota samples Medical Valley: Molybdenum and technetium Photon Interaction Coefficients of Technetium Technetium-MDP Chemistry & Pharmacology Technetium Detection and Containment Return Sources for the information on this website include: Lide, David R., ed. CRC Handbook of Chemistry and Physics, 78th Ed., 1997-1998.

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