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| Atomic symbol: Np |
| Atomic number: 93 |
| Atomic weight: 237.0482 |
| Atomic volume: 11.62 cm3/mol |
| Density: 20.45 g/cm3 |
| Period Number: 7 |
| Group number: none |
| Group name: Rare Earth, Actinides |
| Element classification: Metal |
| Phase at room temperature: Solid |
| Melting Point: 913.2 K |
| Boiling point: 4175 K |
| Heat of fusion: 5.190 kJ/mol |
| Heat of vaporization: ? |
| Ionization Energy: 6.266 eV |
| 1st ionization energy: 597 kJ/mole |
| 2nd ionization energy: kJ/mole |
| 3rd ionization energy: kJ/mole |
| Electronegativity: 1.3 |
| Electron affinity: kJ/mole |
| Specific heat: 0.12 J/gK |
| Heat atomization: kJ/mole atoms |
| Shells: 2,8,18,32,23,8,2 |
| Electron Shell Configuration: [Rn] 5f4 6d1 7s2 |
| Minimum oxidation number: 0 |
| Maximum oxidation number: 7 |
| Minimum common oxidation number: 0 |
| Maximum common oxidation no: 5 |
Appearance & Characteristics |
| Structure:: special:complex |
| Color: silvery |
| Hardness: mohs |
| Toxicity: ? |
| Characteristics: Radioactive |
| Uses: ? |
| Reaction with air: ? |
| Reaction with 6M HCl: ? |
| Reaction with 15M HNO3: ? |
| Reaction with 6M NaOH: ? |
| Number of isotopes: 0 |
| Oxide(s): NpO NpO2 Np2O5 |
| Hydride(s): NpH2 NpH3 |
| Chloride(s): NpCl3 NpCl4 |
| Atomic Radius: 155 pm |
| Ionic radius (1- ion): pm |
| Ionic radius (1+ ion): pm |
| Ionic radius (2- ion): pm |
| Ionic radius (2+ ion): 124 pm |
| Ionic radius (3+ ion): 115 pm |
| Thermal conductivity: 6.3 J/m-sec-deg |
| Electrical conductivity: 1/mohm-cm |
| Polarizability: 24.8 A^3 |
| Source: Synthetic |
| Relative abundance solar system: log |
| Abundance earth's crust: log |
| Estimated crustal abundance: Not Applicable |
| Estimated oceanic abundance: Not Applicable |
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| (Planet Neptune) Neptunium was the first synthetic transuranium element of the actinide series discovered; the isotope 239Np was produced by McMillan and Abelson in 1940 at Berkeley, California, as the result of bombarding uranium with cyclotron-produced neutrons. The isotope 237Np (half-life of 2.14 x 106 years) is currently obtained in gram quantities as a by-product from nuclear reactors in the production of plutonium. Trace quantities of the element are actually found in nature due to transmutation reactions in uranium ores produced by the neutrons which are present. Neptunium is prepared by the reduction of NpF3 with barium or lithium vapor at about 12000C. Neptunium metal has a silvery appearance, is chemically reactive, and exists in at least three structural modifications: alpha-neptunium, orthorhombic, density 20.25 g/cm3, beta-neptunium (above 2800C), tetragonal, density (3130C) 19.36 g/cm3, gamma-neptunium (above 5770C), cubic, density (6000C) 18.0 g/cm3. Neptunium has four ionic oxidation states in solution: Np+3 (pale purple), analogous to the rare earth ion Pm+3, Np+4 (yellow green); NpO2+ (green blue): and NpO2++ (pale pink). These latter oxygenated species are in contrast to the rare earths which exhibit only simple ions of the (II), (III), and (IV) oxidation states in aqueous solution. The element forms tri- and tetrahalides such as NpF3, NpF4, NpCl4, NpBr3, NpI3, and oxides of the various compositions such as are found in the uranium-oxygen system, including Np3O8 and NpO2. Seventeen isotopes of neptunium are now recognized. The Oak Ridge National Laboratory has 237Np available for sale to its licensees and for export. This isotope can be used as a component in neutron detection instruments. |
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