Name: Promethium  Acid-Base Properties: Basic  Atomic Number: 61  Atomic Radius: 2.62 Angstrom  Atomic Symbol: Pm  Atomic Volume: 22.39 cc/mole  Boiling Point: 3785 K  Covalent Radius: 1.63 Angstrom  Crystal Structure: Hexagonal  Density: 6.475 g/cc at 300 K  Electrical Conductivity: - Mmho/cm  Electron Configuration: [Xe] 4f5 6s2  First Ionization Potential: 5.55 V  Heat of Fusion: - kJ/mole  Heat of Vaporization: - kJ/mole  Melting Point: 1204 K  Natural State: Synthetic  Oxidation States: 3  Pauling Electronegativity: 1.13  Specific Heat Capacity: - J/g-K  Thermal Conductivity: 0.18 W/cm-K  Weight: 145 g/mole

History:  In 1902 Branner predicted the existence of an element between neodymium and samarium, and this was confirmed by Moseley in 1914. In 1941, workers at Ohio State University irradiated neodymium and praseodymium with neutrons, deuterons, and alpha particles, and produced several new radioactivities, which most likely were those of element 61. Wu and Segre, and Bethe, in 1942, confirmed the formation; however, chemical proof of the production of element 61 was lacking because of the difficulty in separating the rare earths from each other at that time. In 1945, Marinsky, Glendenin, and Coryell made the first chemical identification by use of ion-exchange chromatography. Their work was doen by fission of uranium and by neutron bombardment of neodymium