Neptunium Facts - Periodic Table of the Elements

Neptunium Facts - Periodic Table of the Elements Neptunium  Basic Facts    Atomic Number: 93 Symbol: Np Atomic Weight: 237.0482 Discovery: E.M. McMillan and P.H. Abelson 1940 (United States) Electron Configuration: [Rn] 5f4 6d1 7s2 Word Origin: Named after the planet Neptune. Isotopes: 20 isotopes of Neptunium are known. The most stable of these is neptunium-237, with a half-life of 2.14 million years Properties: Neptunium has a melting point of 913.2 K, boiling point of 4175 K, heat of fusion of 5.190 kJ/mol, sp. gr. 20.25 at 20 °C; valence 3, 4, 5, or 6. Neptunium is a silvery, ductile, radioactive metal. Three allotropes are known. At room temperature it exists primarily in an orthorhombic crystalline state. Uses: Neptunium-237 is used in neutron-detection equipment. Sources McMillan and Abelson produced neptunium-239 (half-life 2.3 days) by bombarding uranium with neutrons from a cyclotron at the U. of California at Berkeley. Neptunium is also found in very small quantities associated with uranium ores. Element Classification: Radioactive Rare Earth Element (Actinide Series) Density (g/cc): 20.25 Neptunium  Physical Data Melting Point (K): 913 Boiling Point (K): 4175 Appearance: silvery metal Atomic Radius (pm): 130 Atomic Volume (cc/mol): 21.1 Ionic Radius: 95 (4e) 110 (3e) Fusion Heat (kJ/mol): (9.6) Evaporation Heat (kJ/mol): 336 Pauling Negativity Number: 1.36 Oxidation States: 6, 5, 4, 3 Lattice Structure: Orthorhombic Lattice Constant (Ã…): 4.720 References: Los Alamos National Laboratory (2001), Crescent Chemical Company (2001), Langes Handbook of Chemistry (1952), CRC Handbook of Chemistry Physics (18th Ed.) Return to the Periodic Table Periodic Table of the Elements Chemistry Encyclopedia