Praseodymium

Praseodymium,  ₅₉Pr

General properties
Name, symbol	Praseodymium, Pr
Appearance	Gray-white
Praseodymium in the periodic table
- ↑ Pr ↓ Pa Cerium ← Praseodymium → Neodymium
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.

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

• Praseodymium Oxide