Hafnium

  • hafnium, 72hf
    hf-crystal bar.jpg
    hafnium
    pronunciationm/ (haf-nee-əm)
    appearancesteel gray
    standard atomic weight ar, std(hf)178.486(6)[1]
    hafnium 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
    zr

    hf

    rf
    lutetiumhafniumtantalum
    atomic number (z)72
    groupgroup 4
    periodperiod 6
    blockd-block
    element category  transition metal
    electron configuration[xe] 4f14 5d2 6s2
    electrons per shell2, 8, 18, 32, 10, 2
    physical properties
    phase at stpsolid
    melting point2506 k ​(2233 °c, ​4051 °f)
    boiling point4876 k ​(4603 °c, ​8317 °f)
    density (near r.t.)13.31 g/cm3
    when liquid (at m.p.)12 g/cm3
    heat of fusion27.2 kj/mol
    heat of vaporization648 kj/mol
    molar heat capacity25.73 j/(mol·k)
    vapor pressure
    p (pa) 1 10 100 1 k 10 k 100 k
    at t (k) 2689 2954 3277 3679 4194 4876
    atomic properties
    oxidation states−2, +1, +2, +3, +4 (an amphoteric oxide)
    electronegativitypauling scale: 1.3
    ionization energies
    • 1st: 658.5 kj/mol
    • 2nd: 1440 kj/mol
    • 3rd: 2250 kj/mol
    atomic radiusempirical: 159 pm
    covalent radius175±10 pm
    color lines in a spectral range
    spectral lines of hafnium
    other properties
    natural occurrenceprimordial
    crystal structurehexagonal close-packed (hcp)
    hexagonal close packed crystal structure for hafnium
    speed of sound thin rod3010 m/s (at 20 °c)
    thermal expansion5.9 µm/(m·k) (at 25 °c)
    thermal conductivity23.0 w/(m·k)
    electrical resistivity331 nΩ·m (at 20 °c)
    magnetic orderingparamagnetic[2]
    magnetic susceptibility+75.0·10−6 cm3/mol (at 298 k)[3]
    young's modulus78 gpa
    shear modulus30 gpa
    bulk modulus110 gpa
    poisson ratio0.37
    mohs hardness5.5
    vickers hardness1520–2060 mpa
    brinell hardness1450–2100 mpa
    cas number7440-58-6
    history
    namingafter hafnia. latin for: copenhagen, where it was discovered
    predictiondmitri mendeleev (1869)
    discovery and first isolationdirk coster and george de hevesy (1922)
    main isotopes of hafnium
    iso­tope abun­dance half-life (t1/2) decay mode pro­duct
    172hf syn 1.87 y ε 172lu
    174hf 0.16% 2×1015 y α 170yb
    176hf 5.26% stable
    177hf 18.60% stable
    178hf 27.28% stable
    178m2hf syn 31 y it 178hf
    179hf 13.62% stable
    180hf 35.08% stable
    182hf syn 8.9×106 y β 182ta
    category category: hafnium
    | references

    hafnium is a chemical element with the symbol hf and atomic number 72. a lustrous, silvery gray, tetravalent transition metal, hafnium chemically resembles zirconium and is found in many zirconium minerals. its existence was predicted by dmitri mendeleev in 1869, though it was not identified until 1923, by coster and hevesy, making it the last stable element to be discovered. hafnium is named after hafnia, the latin name for copenhagen, where it was discovered.[4][5]

    hafnium is used in filaments and electrodes. some semiconductor fabrication processes use its oxide for integrated circuits at 45 nm and smaller feature lengths. some superalloys used for special applications contain hafnium in combination with niobium, titanium, or tungsten.

    hafnium's large neutron capture cross section makes it a good material for neutron absorption in control rods in nuclear power plants, but at the same time requires that it be removed from the neutron-transparent corrosion-resistant zirconium alloys used in nuclear reactors.

  • characteristics
  • production
  • chemical compounds
  • history
  • applications
  • precautions
  • see also
  • references
  • external links

Hafnium, 72Hf
Hf-crystal bar.jpg
Hafnium
Pronunciationm/ (HAF-nee-əm)
Appearancesteel gray
Standard atomic weight Ar, std(Hf)178.486(6)[1]
Hafnium 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
Zr

Hf

Rf
lutetiumhafniumtantalum
Atomic number (Z)72
Groupgroup 4
Periodperiod 6
Blockd-block
Element category  Transition metal
Electron configuration[Xe] 4f14 5d2 6s2
Electrons per shell2, 8, 18, 32, 10, 2
Physical properties
Phase at STPsolid
Melting point2506 K ​(2233 °C, ​4051 °F)
Boiling point4876 K ​(4603 °C, ​8317 °F)
Density (near r.t.)13.31 g/cm3
when liquid (at m.p.)12 g/cm3
Heat of fusion27.2 kJ/mol
Heat of vaporization648 kJ/mol
Molar heat capacity25.73 J/(mol·K)
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 2689 2954 3277 3679 4194 4876
Atomic properties
Oxidation states−2, +1, +2, +3, +4 (an amphoteric oxide)
ElectronegativityPauling scale: 1.3
Ionization energies
  • 1st: 658.5 kJ/mol
  • 2nd: 1440 kJ/mol
  • 3rd: 2250 kJ/mol
Atomic radiusempirical: 159 pm
Covalent radius175±10 pm
Color lines in a spectral range
Spectral lines of hafnium
Other properties
Natural occurrenceprimordial
Crystal structurehexagonal close-packed (hcp)
Hexagonal close packed crystal structure for hafnium
Speed of sound thin rod3010 m/s (at 20 °C)
Thermal expansion5.9 µm/(m·K) (at 25 °C)
Thermal conductivity23.0 W/(m·K)
Electrical resistivity331 nΩ·m (at 20 °C)
Magnetic orderingparamagnetic[2]
Magnetic susceptibility+75.0·10−6 cm3/mol (at 298 K)[3]
Young's modulus78 GPa
Shear modulus30 GPa
Bulk modulus110 GPa
Poisson ratio0.37
Mohs hardness5.5
Vickers hardness1520–2060 MPa
Brinell hardness1450–2100 MPa
CAS Number7440-58-6
History
Namingafter Hafnia. Latin for: Copenhagen, where it was discovered
PredictionDmitri Mendeleev (1869)
Discovery and first isolationDirk Coster and George de Hevesy (1922)
Main isotopes of hafnium
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct
172Hf syn 1.87 y ε 172Lu
174Hf 0.16% 2×1015 y α 170Yb
176Hf 5.26% stable
177Hf 18.60% stable
178Hf 27.28% stable
178m2Hf syn 31 y IT 178Hf
179Hf 13.62% stable
180Hf 35.08% stable
182Hf syn 8.9×106 y β 182Ta
Category Category: Hafnium
| references

Hafnium is a chemical element with the symbol Hf and atomic number 72. A lustrous, silvery gray, tetravalent transition metal, hafnium chemically resembles zirconium and is found in many zirconium minerals. Its existence was predicted by Dmitri Mendeleev in 1869, though it was not identified until 1923, by Coster and Hevesy, making it the last stable element to be discovered. Hafnium is named after Hafnia, the Latin name for Copenhagen, where it was discovered.[4][5]

Hafnium is used in filaments and electrodes. Some semiconductor fabrication processes use its oxide for integrated circuits at 45 nm and smaller feature lengths. Some superalloys used for special applications contain hafnium in combination with niobium, titanium, or tungsten.

Hafnium's large neutron capture cross section makes it a good material for neutron absorption in control rods in nuclear power plants, but at the same time requires that it be removed from the neutron-transparent corrosion-resistant zirconium alloys used in nuclear reactors.