|
43
Tc
(98)
|
A red giant star. Technetium was once thought to exist only as a synthetic element.
Its spectral lines have now been observed in red giant stars.
Tiny amounts also exist in uranium ores. Image by
NASA/ESA.
| Classification: | Technetium is a transition metal |
| Color: | silver-gray |
| Atomic weight: | (98), no stable isotopes |
| State: | solid |
| Melting point: | 2160 oC, 2433 K |
| Boiling point: | 4260 oC, 4533 K |
| Shells: | 2,8,18,14,1 |
| Electron configuration: | [Kr] 4d6 5s1 |
| Density @ 20oC: | 11.5 g/cm3 |
| Atomic volume: | 8.5 cm3/mol |
| Structure: | hcp: hexagonal close packed |
Discovery of Technetium
Technetium was discovered by Carlo Perrier and Emilio Segrè in Italy in 1937.
They found the technetium-97 isotope in a sample of molybdenum which had been bombarded with deuterium nuclei.
Technetium was the first element to be produced synthetically.
The element is named after the Greek word 'technètos' meaning artificial.
Appearance & Characteristics
A gamma camera and its nuclear medicine operator. Image by Brendaicm.
Harmful effects:
Technetium is harmful due to its radioactivity.
Characteristics:
Technetium is a rare, silver-gray metal that tarnishes slowly in moist air. In powder form, it burns in oxygen to the heptoxide (Tc2O7). Technetium dissolves in nitric acid and concentrated sulfuric acid, but is not soluble in hydrochloric acid of any strength. Is an excellent superconductor at temperatures of 11 K and below. Technetium and promethium are notable among the light elements because they both have no stable isotopes.
Technetium-99m is a metastable isotope with a half-life of six hours. Technetium-99m emits gamma rays and low energy electrons, forming technetium-99 (half-life 211 000 years). The gamma rays can be photographed using a gamma camera, and technetium-99m is used in 80 to 90 percent of all diagnostic procedures that use radioactive elements.
Technetium-95, with a half-life of 61 days, is used as a radioactive tracer. Technetium-99, has a very long half-life (2.11 X 105 years) and decays almost entirely by beta decay with no gamma rays. It is used as for equipment calibration. In small concentrations the pertechnetate ion (TcO 4-) can protect carbon steels and iron from corrosion. This use is limited to closed systems due to its radioactivity.
Technetium is harmful due to its radioactivity.
Characteristics:
Technetium is a rare, silver-gray metal that tarnishes slowly in moist air. In powder form, it burns in oxygen to the heptoxide (Tc2O7). Technetium dissolves in nitric acid and concentrated sulfuric acid, but is not soluble in hydrochloric acid of any strength. Is an excellent superconductor at temperatures of 11 K and below. Technetium and promethium are notable among the light elements because they both have no stable isotopes.
Uses of Technetium
Technetium-99m is a metastable isotope with a half-life of six hours. Technetium-99m emits gamma rays and low energy electrons, forming technetium-99 (half-life 211 000 years). The gamma rays can be photographed using a gamma camera, and technetium-99m is used in 80 to 90 percent of all diagnostic procedures that use radioactive elements.
Technetium-95, with a half-life of 61 days, is used as a radioactive tracer. Technetium-99, has a very long half-life (2.11 X 105 years) and decays almost entirely by beta decay with no gamma rays. It is used as for equipment calibration. In small concentrations the pertechnetate ion (TcO 4-) can protect carbon steels and iron from corrosion. This use is limited to closed systems due to its radioactivity.
Abundance & Isotopes
Abundance earth's crust: negligible
Abundance solar system: negligible
Cost, pure: per 100g
Cost, bulk: per 100g
Source: Technetium has been found naturally occurring in tiny quantities in uranium ore. The isotope technetium-99 is produced from the waste products of uranium nuclear fuel. Technetium-99m is produced by neutron activation of molybdenum-98 to form molybdenum-99, which has a half-life of 65.94 hours and beta-decays to technetium-99m. The spectral signature of technetium has been detected in light from red giant stars.
Isotopes: Technetium has 26 isotopes whose half-lives are known, with mass numbers from 88 to 113. None are stable. The most stable and most common isotope is 99Tc, with a half-life of 2.11 X 105 years.
Abundance solar system: negligible
Cost, pure: per 100g
Cost, bulk: per 100g
Source: Technetium has been found naturally occurring in tiny quantities in uranium ore. The isotope technetium-99 is produced from the waste products of uranium nuclear fuel. Technetium-99m is produced by neutron activation of molybdenum-98 to form molybdenum-99, which has a half-life of 65.94 hours and beta-decays to technetium-99m. The spectral signature of technetium has been detected in light from red giant stars.
Isotopes: Technetium has 26 isotopes whose half-lives are known, with mass numbers from 88 to 113. None are stable. The most stable and most common isotope is 99Tc, with a half-life of 2.11 X 105 years.
Energies
Specific heat capacity: 0.21 J g-1 K-1
Heat of fusion: 24.0 kJ mol-1
1st ionization energy: 702.4 kJ mol-1
3rd ionization energy: 2850.2 kJ mol-1
Heat of fusion: 24.0 kJ mol-1
1st ionization energy: 702.4 kJ mol-1
3rd ionization energy: 2850.2 kJ mol-1
Heat of atomization: 661 kJ mol-1
Heat of vaporization: 502 kJ mol-1
2nd ionization energy: 1472.4 kJ mol-1
Electron affinity: 53 kJ mol-1
Heat of vaporization: 502 kJ mol-1
2nd ionization energy: 1472.4 kJ mol-1
Electron affinity: 53 kJ mol-1
Oxidation & Electrons
Shells: 2,8,18,14,1
Minimum oxidation number: -3
Min. common oxidation no.: 0
Electronegativity (Pauling Scale): 1.9
Minimum oxidation number: -3
Min. common oxidation no.: 0
Electronegativity (Pauling Scale): 1.9
Electron configuration: [Kr] 4d6 5s1
Maximum oxidation number: 7
Max. common oxidation no.: 7
Polarizability volume: 11.4 Å3
Maximum oxidation number: 7
Max. common oxidation no.: 7
Polarizability volume: 11.4 Å3
Reactions & Compounds
Reaction with air: mild, w/ht, ⇒ Tc2O7
Reaction with 15 M HNO3: mild, ⇒ HTcO4 (Pertechnetic acid)
Oxide(s): TcO2, Tc2O7
Hydride(s): none
Reaction with 15 M HNO3: mild, ⇒ HTcO4 (Pertechnetic acid)
Oxide(s): TcO2, Tc2O7
Hydride(s): none
Reaction with 6 M HCl: none
Reaction with 6 M NaOH:
Chloride(s): TcCl4, TcCl6
Reaction with 6 M NaOH:
Chloride(s): TcCl4, TcCl6
Radius
Atomic radius: 136 pm
Ionic radius (2+ ion): pm
Ionic radius (2- ion): pm
Ionic radius (2+ ion): pm
Ionic radius (2- ion): pm
Ionic radius (1+ ion): pm
Ionic radius (3+ ion): 83 pm
Ionic radius (1- ion): pm
Ionic radius (3+ ion): 83 pm
Ionic radius (1- ion): pm
Conductivity
Thermal conductivity: 50.6 W m-1 K-1
Electrical conductivity: 0.001 x 106 S m-1
References
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