Praseodymium

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Praseodymium,  59Pr
General properties
Name, symbol Praseodymium, Pr
Appearance Gray-white
Praseodymium in the periodic table
-

Pr

Pa
CeriumPraseodymiumNeodymium
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)
· references

Praseodymium is a chemical element with the atomic number 59 and symbol Pr, a lanthanide.

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.

References

Relevant Sciencemadness threads