Technetium is an artificial element and was discovered in 1937. It is radioactive and have the greatest number of radioactive isotopes among the lightest elements of the periodic table.
History and Discovery
Technetium was predicted by Dmitri Mendeleev and he assumed that the gap in the periodic table with be filled by an element that would have properties like manganese. Thus, the name ekamanganese was given to the unknown element. In 1937, the first artificial element, technetium-97 was successfully synthesized in the laboratory. The name technetium has been derived from Greek word that means artificial or synthetic [1]. Its symbol is Tc.
Technetium
| Periodic Table Classification | Group 7 Period 5 |
|---|---|
| State at 20C | Solid |
| Color | Shiny gray metal |
| Electron Configuration | [Kr] 4d5 5s2 |
| Electron Number | 43 |
| Proton Number | 43 |
| Electron Shell | 2, 8, 18, 13, 2 |
| Density | 11.5 g.cm-3 at 20°C |
| Atomic number | 43 |
| Atomic Mass | 98.00 g.mol -1 |
| Electronegativity according to Pauling | 1.90 |
Occurrence
Technetium occur in nature in very minute concentrations, around 0.003 parts per trillion of the earth’s crust. It is highly unstable nature and have a half-life of around 4.2 million years, which shows the probability that not even one atom of technetium of the primordial period has survived. At any given time only 18000 tons of technetium is present in the earth’s crust. In nature, it is produced during the radioactive decay of thorium and uranium ores. It has been estimated that one kilogram of uranium will produce around 1 nanogram of technetium [2]. Most of the technetium that is used for various purposes is artificially produced in laboratories. Technetium is produced in bulk amounts during the fission of uranium-235 in nuclear reactors [3]. The largest producers of technetium are Canada and Netherlands where it is produced in the nuclear reactor laboratories. Technium-99 is the commercially significant isotope of technetium, and it is produced by the fission reaction of plutonium or uranium.
Physical Characteristics
Technetium is a silver-grey metal with a lustrous shine. It is the lightest element that have isotopes that all are radioactive, except one. When exposed to air, the metal is tarnished, and a dark oxide layer is formed on the surface of the metal. strontium resembles barium and calcium in most of its physical and chemical properties. It has an atomic number of 43.
Chemical Characteristics
Technetium is a chemically inert element. Technetium has chemical properties that are intermediate between rhenium and manganese and are more like rhenium [4]. Technetium forms stable covalent bonds. It does not readily form cations. There are nine oxidation states of technetium -1 to +7. And the most common are +4, +5 and +7. Technetium does not dissolve in hydrochloric acid but dissolves in aqua regia, sulfuric acid and nitric acid [5]. In powder form, technetium burns in the presence of oxygen.
Significance and Uses
- The nuclear isotope of technetium, technitium-99m, is widely used in nuclear medicine to diagnose various cancers and tumors.
- Technetium is used a catalyst in various industrially significant reactions.
- Technetium have been categorized as potentially useful candidate for making nanoscale nuclear batteries and optoelectronic devices.
Health Hazards
The radioactive waste from the nuclear reactors contain the technetium isotope that is quite stable and has a long half-life, technetium-99. This isotope can leach into soil and plants and can cause health hazards. Individuals handling techniteum-99 should use personal protection kit to avoid inhalation of technetium dust as it can lead to lung cancer.
Isotopes of Technetium
The common natural isotope of technetium is technetium- 99. The most stable radioactive isotope is tenchiteium-98 that has a half-life of 4.2 million years, and techteiun-97 and tenchitium-99 with half-lives of 2.6 Ma and 211,000 years [6].
REFERENCES
[1]. Jonge; Pauwels, E. K. (1996). “Technetium, the missing element”. European Journal of Nuclear Medicine. 23 (3): 336–44. doi:10.1007/BF00837634. PMID 8599967.
[2]. Curtis, D.; Fabryka-Martin, June; Dixon, Paul; Cramer, Jan (1999). “Nature’s uncommon elements: plutonium and technetium”. Geochimica et Cosmochimica Acta. 63 (2): 275. Bibcode:1999GeCoA..63..275C. doi:10.1016/S0016-7037(98)00282-8.
[3]. Rimshaw, S. J. (1968). Hampel, C. A., ed. The Encyclopedia of the Chemical Elements. New York: Reinhold Book Corporation. pp. 689–693
[4]. Greenwood 1997, p. 1044
[5]. Hammond, C. R. (2004). “The Elements”. Handbook of Chemistry and Physics (81st ed.). CRC press. ISBN 0-8493-0485-7.
[6]. NNDC contributors (2008). Sonzogni, A. A., ed. “Chart of Nuclides”. New York: National Nuclear Data Center, Brookhaven National Laboratory. Retrieved 2009-11-11