Protactinium

  • protactinium, 91pa
    protactinium.jpg
    protactinium
    pronunciationm/ (tin-ee-əm)
    appearancebright, silvery metallic luster
    standard atomic weight ar, std(pa)231.03588(1)[1]
    protactinium 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
    pr

    pa

    (uqp)
    thoriumprotactiniumuranium
    atomic number (z)91
    groupgroup n/a
    periodperiod 7
    blockf-block
    element category  actinide
    electron configuration[rn] 5f2 6d1 7s2
    electrons per shell2, 8, 18, 32, 20, 9, 2
    physical properties
    phase at stpsolid
    melting point1841 k ​(1568 °c, ​2854 °f)
    boiling point4300 k ​(4027 °c, ​7280 °f) (?)
    density (near r.t.)15.37 g/cm3
    heat of fusion12.34 kj/mol
    heat of vaporization481 kj/mol
    atomic properties
    oxidation states+2, +3, +4, +5 (a weakly basic oxide)
    electronegativitypauling scale: 1.5
    ionization energies
    • 1st: 568 kj/mol
    atomic radiusempirical: 163 pm
    covalent radius200 pm
    color lines in a spectral range
    spectral lines of protactinium
    other properties
    natural occurrencefrom decay
    crystal structurebody-centered tetragonal[2]
    body-centered tetragonal crystal structure for protactinium
    thermal expansion~9.9 µm/(m·k)[3] (at r.t.)
    thermal conductivity47 w/(m·k)
    electrical resistivity177 nΩ·m (at 0 °c)
    magnetic orderingparamagnetic[4]
    cas number7440-13-3
    history
    predictiondmitri mendeleev (1869)
    discovery and first isolationkasimir fajans and oswald helmuth göhring (1913)
    named byotto hahn and lise meitner (1917–8)
    main isotopes of protactinium
    iso­tope abun­dance half-life (t1/2) decay mode pro­duct
    229pa syn 1.5 d ε 229th
    230pa syn 17.4 d ε 230th
    231pa 100% 3.276×104 y α 227ac
    232pa syn 1.31 d β 232u
    233pa trace 26.967 d β 233u
    234pa trace 6.75 h β 234u
    234mpa trace 1.17 min β 234u
    category category: protactinium
    | references

    protactinium (formerly protoactinium) is a chemical element with the symbol pa and atomic number 91. it is a dense, silvery-gray actinide metal which readily reacts with oxygen, water vapor and inorganic acids. it forms various chemical compounds in which protactinium is usually present in the oxidation state +5, but it can also assume +4 and even +3 or +2 states. concentrations of protactinium in the earth's crust are typically a few parts per trillion, but may reach up to a few parts per million in some uraninite ore deposits. because of its scarcity, high radioactivity and high toxicity, there are currently no uses for protactinium outside scientific research, and for this purpose, protactinium is mostly extracted from spent nuclear fuel.

    protactinium was first identified in 1913 by kasimir fajans and oswald helmuth göhring and named brevium because of the short half-life of the specific isotope studied, i.e. protactinium-234. a more stable isotope of protactinium, 231pa, was discovered in 1917/18 by otto hahn and lise meitner, and they chose the name proto-actinium, but the iupac finally named it "protactinium" in 1949 and confirmed hahn and meitner as discoverers. the new name meant "(nuclear) precursor[5] of actinium" and reflected that actinium is a product of radioactive decay of protactinium. john arnold cranston (working with frederick soddy and ada hitchins) is also credited with discovering the most stable isotope in 1915, but delayed his announcement due to being called up for service in the first world war.[6]

    the longest-lived and most abundant (nearly 100%) naturally occurring isotope of protactinium, protactinium-231, has a half-life of 32,760 years and is a decay product of uranium-235. much smaller trace amounts of the short-lived protactinium-234 and its nuclear isomer protactinium-234m occur in the decay chain of uranium-238. protactinium-233 results from the decay of thorium-233 as part of the chain of events used to produce uranium-233 by neutron irradiation of thorium-232. it is an undesired intermediate product in thorium-based nuclear reactors and is therefore removed from the active zone of the reactor during the breeding process. analysis of the relative concentrations of various uranium, thorium and protactinium isotopes in water and minerals is used in radiometric dating of sediments which are up to 175,000 years old and in modeling of various geological processes.

  • history
  • isotopes
  • occurrence
  • preparation
  • physical and chemical properties
  • chemical compounds
  • applications
  • precautions
  • see also
  • references
  • bibliography
  • external links

Protactinium, 91Pa
Protactinium.jpg
Protactinium
Pronunciationm/ (TIN-ee-əm)
Appearancebright, silvery metallic luster
Standard atomic weight Ar, std(Pa)231.03588(1)[1]
Protactinium 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
Pr

Pa

(Uqp)
thoriumprotactiniumuranium
Atomic number (Z)91
Groupgroup n/a
Periodperiod 7
Blockf-block
Element category  Actinide
Electron configuration[Rn] 5f2 6d1 7s2
Electrons per shell2, 8, 18, 32, 20, 9, 2
Physical properties
Phase at STPsolid
Melting point1841 K ​(1568 °C, ​2854 °F)
Boiling point4300 K ​(4027 °C, ​7280 °F) (?)
Density (near r.t.)15.37 g/cm3
Heat of fusion12.34 kJ/mol
Heat of vaporization481 kJ/mol
Atomic properties
Oxidation states+2, +3, +4, +5 (a weakly basic oxide)
ElectronegativityPauling scale: 1.5
Ionization energies
  • 1st: 568 kJ/mol
Atomic radiusempirical: 163 pm
Covalent radius200 pm
Color lines in a spectral range
Spectral lines of protactinium
Other properties
Natural occurrencefrom decay
Crystal structurebody-centered tetragonal[2]
Body-centered tetragonal crystal structure for protactinium
Thermal expansion~9.9 µm/(m·K)[3] (at r.t.)
Thermal conductivity47 W/(m·K)
Electrical resistivity177 nΩ·m (at 0 °C)
Magnetic orderingparamagnetic[4]
CAS Number7440-13-3
History
PredictionDmitri Mendeleev (1869)
Discovery and first isolationKasimir Fajans and Oswald Helmuth Göhring (1913)
Named byOtto Hahn and Lise Meitner (1917–8)
Main isotopes of protactinium
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct
229Pa syn 1.5 d ε 229Th
230Pa syn 17.4 d ε 230Th
231Pa 100% 3.276×104 y α 227Ac
232Pa syn 1.31 d β 232U
233Pa trace 26.967 d β 233U
234Pa trace 6.75 h β 234U
234mPa trace 1.17 min β 234U
Category Category: Protactinium
| references

Protactinium (formerly protoactinium) is a chemical element with the symbol Pa and atomic number 91. It is a dense, silvery-gray actinide metal which readily reacts with oxygen, water vapor and inorganic acids. It forms various chemical compounds in which protactinium is usually present in the oxidation state +5, but it can also assume +4 and even +3 or +2 states. Concentrations of protactinium in the Earth's crust are typically a few parts per trillion, but may reach up to a few parts per million in some uraninite ore deposits. Because of its scarcity, high radioactivity and high toxicity, there are currently no uses for protactinium outside scientific research, and for this purpose, protactinium is mostly extracted from spent nuclear fuel.

Protactinium was first identified in 1913 by Kasimir Fajans and Oswald Helmuth Göhring and named brevium because of the short half-life of the specific isotope studied, i.e. protactinium-234. A more stable isotope of protactinium, 231Pa, was discovered in 1917/18 by Otto Hahn and Lise Meitner, and they chose the name proto-actinium, but the IUPAC finally named it "protactinium" in 1949 and confirmed Hahn and Meitner as discoverers. The new name meant "(nuclear) precursor[5] of actinium" and reflected that actinium is a product of radioactive decay of protactinium. John Arnold Cranston (working with Frederick Soddy and Ada Hitchins) is also credited with discovering the most stable isotope in 1915, but delayed his announcement due to being called up for service in the First World War.[6]

The longest-lived and most abundant (nearly 100%) naturally occurring isotope of protactinium, protactinium-231, has a half-life of 32,760 years and is a decay product of uranium-235. Much smaller trace amounts of the short-lived protactinium-234 and its nuclear isomer protactinium-234m occur in the decay chain of uranium-238. Protactinium-233 results from the decay of thorium-233 as part of the chain of events used to produce uranium-233 by neutron irradiation of thorium-232. It is an undesired intermediate product in thorium-based nuclear reactors and is therefore removed from the active zone of the reactor during the breeding process. Analysis of the relative concentrations of various uranium, thorium and protactinium isotopes in water and minerals is used in radiometric dating of sediments which are up to 175,000 years old and in modeling of various geological processes.