Praseodymium

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 | |||||||||||||||
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Name, Symbol, Number | praseodymium, Pr, 59 | ||||||||||||||
Chemical series | lanthanides | ||||||||||||||
Group, Period, Block | n/a, 6, f | ||||||||||||||
Appearance | grayish white |
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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) |
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Boiling point | 3793K (3520°C, 6368°F) |
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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 | ||||||||||||||
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Atomic properties | |||||||||||||||
Crystal structure | hexagonal | ||||||||||||||
Oxidation states | 3 (mildly basic oxide) |
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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 |
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Thermal conductivity | (300K) 12.5 W·m-1·K-1 | ||||||||||||||
Thermal expansion | (r.t.) (α, poly) 6.7 µm/(m·K) |
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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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