Praseodymium

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Praseodymium is a chemical element that has the symbol Pr and atomic number 59. Praseodymium is a soft silvery metal in the lanthanide group. It is somewhat more resistant to corrosion in air than europium, lanthanum, cerium, or neodymium, but it does develop a green oxide coating that spalls off when exposed to air, exposing more metal to oxidation. For this reason, praseodymium should be stored under a light mineral oil or sealed in glass.

 

General
Name, Symbol, Number praseodymium, Pr, 59
Chemical series lanthanides
Group, Period, Block n/a, 6, f
Appearance grayish white
Standard atomic weight 140.90765(2) g·mol-1
Electrons per shell 2, 8, 18, 21, 8, 2
Physical properties
Phase solid
Density (near r.t.) 6.77 g·cm−3
Liquid density at m.p. 6.50 g·cm−3
Melting point 1208K
(935°C, 1715°F)
Boiling point 3793K
(3520°C, 6368°F)
Heat of fusion 6.89 kJ·mol-1
Heat of vaporization 331 kJ·mol-1
Heat capacity (25°C) 27.20 J·mol-1·K-1
Vapor pressure
P(Pa) 1 10 100 1 k 10 k 100 k
at T(K) 1771 1973 (2227) (2571) (3054) (3779)
Atomic properties
Crystal structure hexagonal
Oxidation states 3
(mildly basic oxide)
Electronegativity 1.13 (Pauling scale)
Ionization energies
(more)
1st: 527 kJ·mol-1
2nd: 1020 kJ·mol-1
3rd: 2086 kJ·mol-1
Atomic radius 185 pm
Atomic radius (calc.) 247 pm
Miscellaneous
Magnetic ordering no data
Electrical resistivity (r.t.) (α, poly)
0.700 µΩ·m
Thermal conductivity (300K) 12.5 W·m-1·K-1
Thermal expansion (r.t.) (α, poly)
6.7 µm/(m·K)
Speed of sound (thin rod) (20 °C) 2280 m/s
Young's modulus (α form) 37.3 GPa
Shear modulus (α form) 14.8 GPa
Bulk modulus (α form) 28.8 GPa
Poisson ratio (α form) 0.281
Vickers hardness 400 MPa
Brinell hardness 481 MPa
CAS registry number 7440-10-0

 

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