Praseodymium
| General properties | |||||
|---|---|---|---|---|---|
| Name, symbol | Praseodymium, Pr | ||||
| Appearance | Gray-white | ||||
| Praseodymium in the periodic table | |||||
| |||||
| Atomic number | 59 | ||||
| Standard atomic weight (Ar) | 140.90766(2) | ||||
| Group, block | , f-block | ||||
| Period | period 6 | ||||
| Electron configuration | [Xe] 4f3 6s2 | ||||
per shell | 2, 8, 18, 21, 8, 2 | ||||
| Physical properties | |||||
| Gray-white | |||||
| Phase | Solid | ||||
| Melting point | 1208 K (935 °C, 1715 °F) | ||||
| Boiling point | 3403 K (3130 °C, 5666 °F) | ||||
| Density near r.t. | 6.77 g/cm3 | ||||
| when liquid, at | 6.50 g/cm3 | ||||
| Heat of fusion | 6.89 kJ/mol | ||||
| Heat of | 331 kJ/mol | ||||
| Molar heat capacity | 27.2 J/(mol·K) | ||||
| pressure | |||||
| Atomic properties | |||||
| Oxidation states | 5, 4, 3, 2 (a mildly basic oxide) | ||||
| Electronegativity | Pauling scale: 1.13 | ||||
| energies |
1st: 527 kJ/mol 2nd: 1020 kJ/mol 3rd: 2086 kJ/mol | ||||
| Atomic radius | empirical: 182 pm | ||||
| Covalent radius | 203±7 pm | ||||
| Miscellanea | |||||
| Crystal structure | Double hexagonal close-packed (dhcp) | ||||
| Speed of sound thin rod | 2280 m/s (at 20 °C) | ||||
| Thermal expansion | 6.7 µm/(m·K) (α, poly) | ||||
| Thermal conductivity | 12.5 W/(m·K) | ||||
| Electrical resistivity | 7·10-7 Ω·m (α, poly) | ||||
| Magnetic ordering | Paramagnetic | ||||
| Young's modulus | 37.3 GPa (α form) | ||||
| Shear modulus | 14.8 GPa (α form) | ||||
| Bulk modulus | 28.8 GPa (α form) | ||||
| Poisson ratio | 0.281 | ||||
| Vickers hardness | 250–745 MPa | ||||
| Brinell hardness | 250–640 MPa | ||||
| CAS Registry Number | 7440-10-0 | ||||
| History | |||||
| Discovery | Carl Auer von Welsbach (1885) | ||||
Praseodymium is a chemical element with the atomic number 59 and symbol Pr, a lanthanide.
Contents
Properties
Chemical
Praseodymium metal tarnishes slowly in air and burns readily at 150 °C to form praseodymium(III,IV) oxide:
- 12 Pr + 11 O2 → 2 Pr6O11
It is somewhat more resistant to corrosion in air than most lanthanides, such as europium, lanthanum, cerium, or neodymium. It will slowly build-up a green oxide coating that spalls off when exposed to air, exposing more metal to oxidation.
Physical
Praseodymium is a silvery, soft, malleable, and ductile lanthanide metal. It will slowly oxidize in air, giving the metal a greenish aspect. It melts at 935 °C and boils at 3130 °C. Its density is 6.77 g/cm3.
Availability
Praseodymium is sold by Metallium and can also be purchased from Ebay.
Preparation
Reducing praseodymium salts with a reactive metal such as calcium or magnesium yields metallic praseodymium.
Projects
- Praseodymium yellow-green glass
- Make didymium
- Make PrNi5 alloy
- Make Pr salts
Handling
Safety
Like all lanthanides, praseodymium has low to moderate toxicity. It has no known biological role.
Storage
Praseodymium should be kept in closed bottles or ampoules, away from moisture or corrosive vapors.
Disposal
Best to try to recycle it.
