• Class: Trans-Uranium AcTinides
• Period: 7
• IUPAC group: 3
• Traditional: IIIa

• Discovered in: 1940 by McMillan, Abelson
• Origin of name: The planet Neptune
• Historical or alternate name:

Traces in Uranium ores

Silvery metal. Resists alkalis; reacts with Oxygen and acids. Attacked by steam.

• Atmosphere: ~0.0 ppm
• Primitive mantle: ~0.0 ppm
• Sea water: ~0.0 ppm
• Metallic meteorite: ~0.0 ppm
• ConTinental crust: ~0.0 ppm
• Solar photosphere: ~0.0 log of abundance
• Oceanic crust: ~0.0 ppm
• Solar system: ~0.0 relative to Si=1.0e6

   Hazards

Radioactive. Radiotoxic..

• Lower:
• Upper:

Neptunium Physical Properties

 Transitional Data

• State: Solid
• Density: 20.45 g/cm3

 Molar enthalpy

• Atomization: 457.0 kJ mol-1
• Fusion: 9.46 kJ mol-1
• Vaporization: 336.6 kJ mol-1

 Transition points

• MelTing point: 913.0 K
• Boiling point: 4175.0 K
• Critical temperature: 12000.0 K

 Molar properties

• Atomic weight: 237.0482 g/mole
• Molar volume: 11.65 cm3 mol-1

 Crystal structure sequence

orthorhombic <553 K < complex-tetragonal < 850 K < body-centered-cubic < melTing point

 Thermodynamics

 Miscellaneous physical

• Electrical resistivity: 122.0 µ-ohms/cm
• Debye temperature: 187.5 K
• Thermal conductivity: 6.3 W / m / K
• Coefficient of linear expansion: 18.0Coef. per K
• Mass magnetic susceptibility:
• X-ray diffraction mass absorption coefficients:
• CuK: (µ/p)/cm2 g-1
• MoK: (µ/p)/cm2 g-1

Neptunium Chemical Properties

 Chemical basics:

• Oxidation states: +2 +3 +4 +5 +6 +7
• Molecular wt: 237.0482 g/mole

 Radii

• Covalent: pm
• Atomic: 155.0 pm
• Van der Waals: pm

 Ions:

• ion: +2 pm 110.0
• ion: +3 pm 101.0
• ion: +4 pm 87.0
• ion: +5 pm 75.0
• ion: +6 pm 72.0
• ion: +7 pm 71.0

 Covalent bonds

 Effective nuclear charge

• Slater: 1.80
• Clementi:
• Froese-Fischer:

 Electronegativity

• Pauling: 1.4
• Allred-Rochow: 1.22

 Standard reactions

Neptunium Nuclear Properties

• Known 15
• Listed 3

• Known 229 - 241
• Listed 235 - 237

• % Occ.:Natural
• Mossbauer NRA:
• Nuclear spin/Quantum no.: 5/2
• Radioisotopes:
  • Half-life: 396.00 days
  • Decay mode: E.C. alpha,
  • Source:
• Notes

• % Occ.:Natural
• Mossbauer NRA:
• Nuclear spin/Quantum no.: 6/0
• Radioisotopes:
  • Half-life: 0.12 E6 years
  • Decay mode: E.C. Beta-
  • Source:
• Notes

• % Occ.:Natural
• Mossbauer NRA: 9.53
• Nuclear spin/Quantum no.: 5/2
• Radioisotopes:
  • Half-life: 2.14 E6 years
  • Decay mode: alpha,
  • Source:
• Notes

• Isotope 237Cross-section 170±5 barns

• Absolute sensitivity: 1H=1.0
• Relative sensitivity: 1H=1.0
• Receptivity: 13C=1.0
• Magnetogyric ratio: 3.1e7 rad / T / s
• Quadropole moment: 4.2e-28 m2
• Frequency: 11.25 MHz
• Reference:

Neptunium Energy Properties

Electrons

• Ground state electron configuration: [Rn] 5f4 6d1 7s2
• Electron affinity: kJ mol-1
• Filling orbitals:

 Ionization energies

 Atomic energy levels