Neptunium

  • neptunium, 93np
    np sphere.jpg
    neptunium
    pronunciationm/ (tew-nee-əm)
    appearancesilvery metallic
    mass number[237]
    neptunium 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
    pm

    np

    (uqs)
    uraniumneptuniumplutonium
    atomic number (z)93
    groupgroup n/a
    periodperiod 7
    blockf-block
    element category  actinide
    electron configuration[rn] 5f4 6d1 7s2
    electrons per shell2, 8, 18, 32, 22, 9, 2
    physical properties
    phase at stpsolid
    melting point912±3 k ​(639±3 °c, ​1182±5 °f)
    boiling point4447 k ​(4174 °c, ​7545 °f) (extrapolated)
    density (near r.t.)alpha: 20.45 g/cm3[1]
    accepted standard value: 19.38 g/cm3
    heat of fusion5.19 kj/mol
    heat of vaporization336 kj/mol
    molar heat capacity29.46 j/(mol·k)
    vapor pressure
    p (pa) 1 10 100 1 k 10 k 100 k
    at t (k) 2194 2437
    atomic properties
    oxidation states+2, +3, +4,[2] +5, +6, +7 (an amphoteric oxide)
    electronegativitypauling scale: 1.36
    ionization energies
    • 1st: 604.5 kj/mol
    atomic radiusempirical: 155 pm
    covalent radius190±1 pm
    color lines in a spectral range
    spectral lines of neptunium
    other properties
    natural occurrencefrom decay
    crystal structureorthorhombic
    orthorhombic crystal structure for neptunium
    thermal conductivity6.3 w/(m·k)
    electrical resistivity1.220 µΩ·m (at 22 °c)
    magnetic orderingparamagnetic[3]
    cas number7439-99-8
    history
    namingafter planet neptune, itself named after roman god of the sea neptune
    discoveryedwin mcmillan and philip h. abelson (1940)
    main isotopes of neptunium
    iso­tope abun­dance half-life (t1/2) decay mode pro­duct
    235np syn 396.1 d α 231pa
    ε 235u
    236np syn 1.54×105 y ε 236u
    β 236pu
    α 232pa
    237np trace 2.144×106 y α 233pa
    239np trace 2.356 d β 239pu
    category category: neptunium
    | references

    neptunium is a chemical element with the symbol np and atomic number 93. a radioactive actinide metal, neptunium is the first transuranic element. its position in the periodic table just after uranium, named after the planet uranus, led to it being named after neptune, the next planet beyond uranus. a neptunium atom has 93 protons and 93 electrons, of which seven are valence electrons. neptunium metal is silvery and tarnishes when exposed to air. the element occurs in three allotropic forms and it normally exhibits five oxidation states, ranging from +3 to +7. it is radioactive, poisonous, pyrophoric, and capable of accumulating in bones, which makes the handling of neptunium dangerous.

    although many false claims of its discovery were made over the years, the element was first synthesized by edwin mcmillan and philip h. abelson at the berkeley radiation laboratory in 1940.[4] since then, most neptunium has been and still is produced by neutron irradiation of uranium in nuclear reactors. the vast majority is generated as a by-product in conventional nuclear power reactors. while neptunium itself has no commercial uses at present, it is used as a precursor for the formation of plutonium-238, used in radioisotope thermal generators to provide electricity for spacecraft. neptunium has also been used in detectors of high-energy neutrons.

    the longest-lived isotope of neptunium, neptunium-237, is a by-product of nuclear reactors and plutonium production. it, and the isotope neptunium-239, are also found in trace amounts in uranium ores due to neutron capture reactions and beta decay.[5]

  • characteristics
  • history
  • production
  • chemistry and compounds
  • applications
  • role in nuclear waste
  • biological role and precautions
  • references
  • bibliography
  • literature
  • external links

Neptunium, 93Np
Np sphere.jpg
Neptunium
Pronunciationm/ (TEW-nee-əm)
Appearancesilvery metallic
Mass number[237]
Neptunium 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
Pm

Np

(Uqs)
uraniumneptuniumplutonium
Atomic number (Z)93
Groupgroup n/a
Periodperiod 7
Blockf-block
Element category  Actinide
Electron configuration[Rn] 5f4 6d1 7s2
Electrons per shell2, 8, 18, 32, 22, 9, 2
Physical properties
Phase at STPsolid
Melting point912±3 K ​(639±3 °C, ​1182±5 °F)
Boiling point4447 K ​(4174 °C, ​7545 °F) (extrapolated)
Density (near r.t.)alpha: 20.45 g/cm3[1]
accepted standard value: 19.38 g/cm3
Heat of fusion5.19 kJ/mol
Heat of vaporization336 kJ/mol
Molar heat capacity29.46 J/(mol·K)
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 2194 2437
Atomic properties
Oxidation states+2, +3, +4,[2] +5, +6, +7 (an amphoteric oxide)
ElectronegativityPauling scale: 1.36
Ionization energies
  • 1st: 604.5 kJ/mol
Atomic radiusempirical: 155 pm
Covalent radius190±1 pm
Color lines in a spectral range
Spectral lines of neptunium
Other properties
Natural occurrencefrom decay
Crystal structureorthorhombic
Orthorhombic crystal structure for neptunium
Thermal conductivity6.3 W/(m·K)
Electrical resistivity1.220 µΩ·m (at 22 °C)
Magnetic orderingparamagnetic[3]
CAS Number7439-99-8
History
Namingafter planet Neptune, itself named after Roman god of the sea Neptune
DiscoveryEdwin McMillan and Philip H. Abelson (1940)
Main isotopes of neptunium
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct
235Np syn 396.1 d α 231Pa
ε 235U
236Np syn 1.54×105 y ε 236U
β 236Pu
α 232Pa
237Np trace 2.144×106 y α 233Pa
239Np trace 2.356 d β 239Pu
Category Category: Neptunium
| references

Neptunium is a chemical element with the symbol Np and atomic number 93. A radioactive actinide metal, neptunium is the first transuranic element. Its position in the periodic table just after uranium, named after the planet Uranus, led to it being named after Neptune, the next planet beyond Uranus. A neptunium atom has 93 protons and 93 electrons, of which seven are valence electrons. Neptunium metal is silvery and tarnishes when exposed to air. The element occurs in three allotropic forms and it normally exhibits five oxidation states, ranging from +3 to +7. It is radioactive, poisonous, pyrophoric, and capable of accumulating in bones, which makes the handling of neptunium dangerous.

Although many false claims of its discovery were made over the years, the element was first synthesized by Edwin McMillan and Philip H. Abelson at the Berkeley Radiation Laboratory in 1940.[4] Since then, most neptunium has been and still is produced by neutron irradiation of uranium in nuclear reactors. The vast majority is generated as a by-product in conventional nuclear power reactors. While neptunium itself has no commercial uses at present, it is used as a precursor for the formation of plutonium-238, used in radioisotope thermal generators to provide electricity for spacecraft. Neptunium has also been used in detectors of high-energy neutrons.

The longest-lived isotope of neptunium, neptunium-237, is a by-product of nuclear reactors and plutonium production. It, and the isotope neptunium-239, are also found in trace amounts in uranium ores due to neutron capture reactions and beta decay.[5]