Promethium
Promethium is a chemical element with the symbol Pm and atomic number 61. It is notable for being the only other radioactive element besides technetium which is followed by chemical elements that have stable isotopes.
| General | |
|---|---|
| Name, Symbol, Number | promethium, Pm, 61 |
| Chemical series | lanthanides |
| Group, Period, Block | n/a, 6, f |
| Appearance | metallic |
| Standard atomic weight | [145](0) g·mol-1 |
| Electrons per shell | 2, 8, 18, 23, 8, 2 |
| Physical properties | |
| Phase | solid |
| Density (near r.t.) | 7.26 g·cm−3 |
| Melting point | 1315K (1042°C, 1908°F) |
| Boiling point | 3273K (3000°C, 5432°F) |
| Heat of fusion | 7.13 kJ·mol-1 |
| Heat of vaporization | 289 kJ·mol-1 |
| Atomic properties | |
| Crystal structure | hexagonal |
| Oxidation states | 3 (mildly basic oxide) |
| Electronegativity | ? 1.13 (Pauling scale) |
| Ionization energies (more) |
1st: 540 kJ·mol-1 |
| 2nd: 1050 kJ·mol-1 | |
| 3rd: 2150 kJ·mol-1 | |
| Atomic radius | 185 pm |
| Atomic radius (calc.) | 205 pm |
| Miscellaneous | |
| Magnetic ordering | no data |
| Electrical resistivity | (r.t.) est. 0.75 µΩ·m |
| Thermal conductivity | (300K) 17.9 W·m-1·K-1 |
| Thermal expansion | (r.t.) (α, poly) est. 11 µm/(m·K) |
| Young's modulus | (α form) est. 46 GPa |
| Shear modulus | (α form) est. 18 GPa |
| Bulk modulus | (α form) est. 33 GPa |
| Poisson ratio | (α form) est. 0.28 |
| CAS registry number | 7440-12-2 |
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