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Neptunium, 93 General properties Pronunciation Template:Infobox element/pronunciation Appearance silvery metallic Standard atomic weight (A r, standard ) Template:Infobox element/standard atomic weight Mass number Template:Infobox element/symbol-to-most-stable-isotope (most stable isotope)Neptunium in the periodic table Template:Infobox element/periodic table Atomic number (Z ) 93 Group Template:Infobox element/group Period period 7 Block f-block Element category Template:Infobox element/category format Electron configuration [Rn ] 5f4 6d1 7s2 Electrons per shell
2, 8, 18, 32, 22, 9, 2 Physical properties Phase at STP solid Melting point 912±3 K (639±3 °C, 1182±5 °F) Boiling point 4447 K (4174 °C, 7545 °F) (extrapolated) Density (near r.t. ) alpha: 20.45 g/cm3 [1] 3 Heat of fusion 5.19 kJ/mol [[Enthalpy of vaporization|Heat of Template:Engvar ]] 336 kJ/mol Molar heat capacity 29.46 J/(mol·K) [[Vapor pressure|Template:Engvar pressure Atomic properties Oxidation states Template:Infobox element/symbol-to-oxidation-state Electronegativity Pauling scale: 1.36 [[Ionization energy|Template:Engvar energies]] Atomic radius empirical: 155 pm Covalent radius 190±1 pm Template:Infobox element/spectral lines Other properties Crystal structure Template:Infobox element/crystal structure Thermal conductivity 6.3 W/(m·K) Electrical resistivity 1.220 µΩ·m (at 22 °C) Magnetic ordering paramagnetic [2] CAS Number 7439-99-8 History Naming after planet Neptune , itself named after Roman god of the sea Neptune Discovery Edwin McMillan and Philip H. Abelson (1940) Main isotopes of neptunium Template:Infobox element/isotopes table | references
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↑ Sanchez, Rene G.; Loaiza, David J.; Kimpland, Robert H.; Hayes, David K.; Cappiello, Charlene C.; Myers, William L.; Jaegers, Peter J.; Clement, Steven D.; Butterfield, Kenneth B. "Criticality of a 237 Np Sphere" (PDF) . Japanese Atomic Energy Agency. Retrieved 2014-08-06 . ↑ Magnetic susceptibility of the elements and inorganic compounds , in Handbook of Chemistry and Physics 81st edition, CRC press. 