| Technetium |
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| Atomic Number - | 43 | Melting Point (°C,°F) - | 2157 °C, 3915 °F |
| Atomic Symbol - | Tc | Boiling Point (°C,°F) - | 4265 °C, 7709 °F |
| Atomic Mass - | (98) | Electron Configuration - | [Kr] 4d5 5s2 |
| Group - | 7 | Electrons Per Shell - | 2, 8, 18, 13, 2 |
| Period - | 5 | Protons - | 43 |
| Series - | Transition Metals | Neutrons - | 55 |
| Block - | f-block | | |
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Element Description - Technetium is a chemical element that has the symbol Tc and the atomic number 43. Pronounced tek-nee-s(h)ee-um, the chemical properties of this silvery grey, radioactive, crystalline transition metal are intermediate between rhenium and manganese. Its short-lived isotope Tc-99m is used in nuclear medicine for a wide variety of diagnostic tests. Tc-99 is used as a gamma ray-free source of beta particles, and its pertechnetate ion (TcO4-) could find use as an anodic corrosion inhibitor for steel.
Dmitri Mendeleev predicted many of the properties of element 43, which he called ekamanganese, well before its actual discovery (see Mendeleev's predicted elements). In 1937 its isotope Tc-97 became the first element to be artificially produced, hence its name (from the Greek ????????, meaning "artificial"). Most technetium produced on Earth is a by-product of fission of uranium-235 in nuclear reactors and is extracted from nuclear fuel rods. No isotope of technetium has a half-life longer than 4.2 million years (Tc-98), so its detection in red giants in 1952 helped bolster the theory that stars can produce heavier elements. On earth, technetium occurs naturally only in uranium ores as a product of spontaneous fission; the quantities are minute but have been measured. |
Element Characteristics - Technetium is a silvery-grey radioactive metal with an appearance similar to platinum. However, it is commonly obtained as a grey powder. Its position in the periodic table is between rhenium and manganese and as predicted by the periodic law its properties are intermediate between those two elements. This element is unusual among the lighter elements because it has no stable isotopes and is therefore extremely rare on Earth.
The metal form of technetium slowly tarnishes in moist air. Its oxides are TcO2 and Tc2O7. Under oxidizing conditions technetium (VII) will exist as the pertechnetate ion, TcO4-. Common oxidation states of technetium include 0, +2, +4, +5, +6 and +7. When in powder form technetium will burn in oxygen. It dissolves in aqua regia, nitric acid, and concentrated sulfuric acid, but it is not soluble in hydrochloric acid. It has characteristic spectral lines at 363 nm, 403 nm, 410 nm, 426 nm, 430 nm, and 485 nm.
The metal form is slightly paramagnetic, meaning its magnetic dipoles align with external magnetic fields even though technetium is not normally magnetic. The crystal structure of the metal is hexagonal close-packed. Pure metallic single-crystal technetium becomes a type II superconductor at 7.46 K; irregular crystals and trace impurities raise this temperature to 11.2 K for 99.9% pure technetium powder. Below this temperature technetium has a very high magnetic penetration depth, the largest among the elements apart from niobium. |
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