Technetium

  • technetium, 43tc
    technetium.jpg
    technetium
    pronunciationəm/ (nee-shee-əm)
    appearanceshiny gray metal
    mass number[97]
    technetium in the periodic table
    hydrogen helium
    lithium beryllium boron carbon nitrogen oxygen fluorine neon
    sodium magnesium aluminium silicon phosphorus sulfur chlorine argon
    potassium calcium scandium titanium vanadium chromium manganese iron cobalt nickel copper zinc gallium germanium arsenic selenium bromine krypton
    rubidium strontium yttrium zirconium niobium molybdenum technetium ruthenium rhodium palladium silver cadmium indium tin antimony tellurium iodine xenon
    caesium barium lanthanum cerium praseodymium neodymium promethium samarium europium gadolinium terbium dysprosium holmium erbium thulium ytterbium lutetium hafnium tantalum tungsten rhenium osmium iridium platinum gold mercury (element) thallium lead bismuth polonium astatine radon
    francium radium actinium thorium protactinium uranium neptunium plutonium americium curium berkelium californium einsteinium fermium mendelevium nobelium lawrencium rutherfordium dubnium seaborgium bohrium hassium meitnerium darmstadtium roentgenium copernicium nihonium flerovium moscovium livermorium tennessine oganesson
    mn

    tc

    re
    molybdenumtechnetiumruthenium
    atomic number (z)43
    groupgroup 7
    periodperiod 5
    blockd-block
    element category  transition metal
    electron configuration[kr] 4d5 5s2
    electrons per shell2, 8, 18, 13, 2
    physical properties
    phase at stpsolid
    melting point2430 k ​(2157 °c, ​3915 °f)
    boiling point4538 k ​(4265 °c, ​7709 °f)
    density (near r.t.)11 g/cm3
    heat of fusion33.29 kj/mol
    heat of vaporization585.2 kj/mol
    molar heat capacity24.27 j/(mol·k)
    vapor pressure (extrapolated)
    p (pa) 1 10 100 1 k 10 k 100 k
    at t (k) 2727 2998 3324 3726 4234 4894
    atomic properties
    oxidation states−3, −1, 0, +1,[1] +2, +3,[1] +4, +5, +6, +7 (a strongly acidic oxide)
    electronegativitypauling scale: 1.9
    ionization energies
    • 1st: 702 kj/mol
    • 2nd: 1470 kj/mol
    • 3rd: 2850 kj/mol
    atomic radiusempirical: 136 pm
    covalent radius147±7 pm
    color lines in a spectral range
    spectral lines of technetium
    other properties
    natural occurrencefrom decay
    crystal structurehexagonal close-packed (hcp)
    hexagonal close packed crystal structure for technetium
    speed of sound thin rod16,200 m/s (at 20 °c)
    thermal expansion7.1 µm/(m·k)[2] (at r.t.)
    thermal conductivity50.6 w/(m·k)
    electrical resistivity200 nΩ·m (at 20 °c)
    magnetic orderingparamagnetic
    magnetic susceptibility+270.0·10−6 cm3/mol (298 k)[3]
    cas number7440-26-8
    history
    predictiondmitri mendeleev (1871)
    discovery and first isolationemilio segrè and carlo perrier (1937)
    main isotopes of technetium
    iso­tope abun­dance half-life (t1/2) decay mode pro­duct
    95mtc syn 61 d ε 95mo
    γ
    it 95tc
    96tc syn 4.3 d ε 96mo
    γ
    97tc syn 4.21×106 y ε 97mo
    97mtc syn 91 d it 97tc
    98tc syn 4.2×106 y β 98ru
    γ
    99tc trace 2.111×105 y β 99ru
    99mtc syn 6.01 h it 99tc
    γ
    category category: technetium
    | references

    technetium is a chemical element with the symbol tc and atomic number 43. it is the lightest element whose isotopes are all radioactive; none are stable other than the fully ionized state of 97tc.[4] nearly all technetium is produced as a synthetic element, and only about 18,000 tons are estimated to exist at any given time in the earth's crust. naturally occurring technetium is a spontaneous fission product in uranium ore and thorium ore, the most common source, or the product of neutron capture in molybdenum ores. this silvery gray, crystalline transition metal lies between manganese and rhenium in group 7 of the periodic table, and its chemical properties are intermediate between those of these two adjacent elements. the most common naturally occurring isotope is 99tc.

    many of technetium's properties were predicted by dmitri mendeleev before the element was discovered. mendeleev noted a gap in his periodic table and gave the undiscovered element the provisional name ekamanganese (em). in 1937, technetium (specifically the technetium-97 isotope) became the first predominantly artificial element to be produced, hence its name (from the greek τεχνητός, meaning "synthetic or artificial", + -ium).

    one short-lived gamma ray-emitting nuclear isomer of technetium—technetium-99m—is used in nuclear medicine for a wide variety of diagnostic tests, such as bone cancer diagnoses. the ground state of this nuclide, technetium-99, is used as a gamma-ray-free source of beta particles. long-lived technetium isotopes produced commercially are by-products of the fission of uranium-235 in nuclear reactors and are extracted from nuclear fuel rods. because no isotope of technetium has a half-life longer than 4.21 million years (technetium-97), the 1952 detection of technetium in red giants helped to prove that stars can produce heavier elements.

  • history
  • characteristics
  • compounds
  • occurrence and production
  • applications
  • precautions
  • notes
  • references
  • bibliography
  • further reading
  • external links

Technetium, 43Tc
Technetium.jpg
Technetium
Pronunciationəm/ (NEE-shee-əm)
Appearanceshiny gray metal
Mass number[97]
Technetium in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson
Mn

Tc

Re
molybdenumtechnetiumruthenium
Atomic number (Z)43
Groupgroup 7
Periodperiod 5
Blockd-block
Element category  Transition metal
Electron configuration[Kr] 4d5 5s2
Electrons per shell2, 8, 18, 13, 2
Physical properties
Phase at STPsolid
Melting point2430 K ​(2157 °C, ​3915 °F)
Boiling point4538 K ​(4265 °C, ​7709 °F)
Density (near r.t.)11 g/cm3
Heat of fusion33.29 kJ/mol
Heat of vaporization585.2 kJ/mol
Molar heat capacity24.27 J/(mol·K)
Vapor pressure (extrapolated)
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 2727 2998 3324 3726 4234 4894
Atomic properties
Oxidation states−3, −1, 0, +1,[1] +2, +3,[1] +4, +5, +6, +7 (a strongly acidic oxide)
ElectronegativityPauling scale: 1.9
Ionization energies
  • 1st: 702 kJ/mol
  • 2nd: 1470 kJ/mol
  • 3rd: 2850 kJ/mol
Atomic radiusempirical: 136 pm
Covalent radius147±7 pm
Color lines in a spectral range
Spectral lines of technetium
Other properties
Natural occurrencefrom decay
Crystal structurehexagonal close-packed (hcp)
Hexagonal close packed crystal structure for technetium
Speed of sound thin rod16,200 m/s (at 20 °C)
Thermal expansion7.1 µm/(m·K)[2] (at r.t.)
Thermal conductivity50.6 W/(m·K)
Electrical resistivity200 nΩ·m (at 20 °C)
Magnetic orderingParamagnetic
Magnetic susceptibility+270.0·10−6 cm3/mol (298 K)[3]
CAS Number7440-26-8
History
PredictionDmitri Mendeleev (1871)
Discovery and first isolationEmilio Segrè and Carlo Perrier (1937)
Main isotopes of technetium
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct
95mTc syn 61 d ε 95Mo
γ
IT 95Tc
96Tc syn 4.3 d ε 96Mo
γ
97Tc syn 4.21×106 y ε 97Mo
97mTc syn 91 d IT 97Tc
98Tc syn 4.2×106 y β 98Ru
γ
99Tc trace 2.111×105 y β 99Ru
99mTc syn 6.01 h IT 99Tc
γ
Category Category: Technetium
| references

Technetium is a chemical element with the symbol Tc and atomic number 43. It is the lightest element whose isotopes are all radioactive; none are stable other than the fully ionized state of 97Tc.[4] Nearly all technetium is produced as a synthetic element, and only about 18,000 tons are estimated to exist at any given time in the Earth's crust. Naturally occurring technetium is a spontaneous fission product in uranium ore and thorium ore, the most common source, or the product of neutron capture in molybdenum ores. This silvery gray, crystalline transition metal lies between manganese and rhenium in group 7 of the periodic table, and its chemical properties are intermediate between those of these two adjacent elements. The most common naturally occurring isotope is 99Tc.

Many of technetium's properties were predicted by Dmitri Mendeleev before the element was discovered. Mendeleev noted a gap in his periodic table and gave the undiscovered element the provisional name ekamanganese (Em). In 1937, technetium (specifically the technetium-97 isotope) became the first predominantly artificial element to be produced, hence its name (from the Greek τεχνητός, meaning "synthetic or artificial", + -ium).

One short-lived gamma ray-emitting nuclear isomer of technetium—technetium-99m—is used in nuclear medicine for a wide variety of diagnostic tests, such as bone cancer diagnoses. The ground state of this nuclide, technetium-99, is used as a gamma-ray-free source of beta particles. Long-lived technetium isotopes produced commercially are by-products of the fission of uranium-235 in nuclear reactors and are extracted from nuclear fuel rods. Because no isotope of technetium has a half-life longer than 4.21 million years (technetium-97), the 1952 detection of technetium in red giants helped to prove that stars can produce heavier elements.