Tc - Technetium
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- Atomic Number: 43
- Atomic Weight (Mass): 98.00000
- Melting Point: 3180 °C
- Boiling Point: 5627 °C
- Orbital Class: 4d
- Orbital: [Kr] 4d5 5s2
- Class: Transition Metals
- Electronegativity: 2.1
- Density: 11 gcm-3
- Van der Waals Radius: .200 nm
- Ionic Radius: unknown
- First Ionization Energy: 702.42 kJ mol-1
- Second Ionization Energy: 702.42 kJ mol-1
- Third Ionization Energy: 2850.20 kJ mol-1
- Heat of Fusion: 23.81 kJ mol-1
- Heat of Vaporization: 585.22 kJ mol-1
- Heat of Atomization: 678 kJ mol-1
- Electrical Conductivity: 16.9 µ Ωcm
- Thermal Conductivity: 50.6 W m-1 K-1
- Related To: Mn, Tc, Re,
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Technetium is a Block D, Group 7, Period 5 element. The electronic configuration is [Kr] 4d5 5s2. In its elemental form Technetium's CAS number is 7440-26-8. The Technetium atom has a radius of 135.2.pm and it's Van der Waals radius is 200.pm.
Technetium was discovered by Carlo Perrier and Emilio Segre in 1937.
French: technetium, German:Technetium, Italian: tecneto, Portuguese: Tecnecio, Spanish: tecnecio, Swedish: Teknetium
This element can be purchased in a variety of forms including as metal, compounds, ultra high purity, nanoparticles, and isotopes at www.americanelements.com
Source: www.americanelements.com
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Technetium is the lightest chemical element with no stable isotope. It has atomic number 43 and is given the symbol Tc. The chemical properties of this silvery grey, crystalline transition metal are intermediate between rhenium and manganese. Its short-lived gamma-emitting isotope 99mTc (technetium-99m) is used in nuclear medicine for a wide variety of diagnostic tests. 99Tc is used as a gamma ray-free source of beta particles. The pertechnetate ion (TcO4-) could find use as an anodic corrosion inhibitor for steel.
Before the element was discovered, many of the properties of element 43 were predicted by Dmitri Mendeleev. Mendeleev noted a gap in his periodic table and called the element ekamanganese. In 1937 its isotope 97Tc became the first predominantly artificial element to be produced, hence its name (from 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 (98Tc), so its detection in red giants in 1952 helped bolster the theory that stars can produce heavier elements. Note that on Earth, technetium occurs in trace but measurable quantities as a product of spontaneous fission in uranium ore or by neutron capture in molybdenum ores.
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, like promethium, is unusual among the lighter elements in that it has no stable isotopes. Only these two elements have no stable isotopes, but are followed by elements which do.
Technetium is therefore extremely rare on Earth. Technetium plays no natural biological role and is not normally found in the human body.
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.
Technetium is produced in quantity by nuclear fission, and spreads more readily than many radionuclides. In spite of the importance of understanding its toxicity in animals and humans, experimental evidence is scant. It appears to have low chemical toxicity. Its radiological toxicity (per unit of mass) is a function of compound, type of radiation for the isotope in question, and the isotope half-life. Technetium-99m is particularly attractive for medical applications, inasmuch as the radiation from this isotope is a gamma ray with the same wavelength as X-rays used for common medical diagnostic X-ray applications, giving it adequate penetration while causing minimal damage for a gamma photon. This, plus the very short half-life of this metastable nuclear isomer, followed by the relatively long half-life of the daughter isotope Tc-99 which allows it to be eliminated from the body before it decays, make for a relatively low dose of administered radiation in biologically dose-equivalent amounts (sieverts) for a typical Tc-99m based nuclear scan (see more on this subject below).
All isotopes of technetium must be handled carefully. The most common isotope, technetium-99, is a weak beta emitter; such radiation is stopped by the walls of laboratory glassware. Soft X-rays are emitted when the beta particles are stopped, but as long as the body is kept more than 30 cm away these should pose no problem. The primary hazard when working with technetium is inhalation of dust; such radioactive contamination in the lungs can pose a significant cancer risk. For most work, careful handling in a fume hood is sufficient; a glove box is not needed.
Source: Wikipedia.org