Praseodymium

59

Pr

140.90765(

  • Name: Praseodymium
  • Symbol: Pr
  • Atomic number: 59
  • Atomic weight: 140.90765(
  • CAS Registry ID: 7440-10-0
  • Group name: Lanthanoid
  • Period number: 6
  • Block: f-block
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Description

Praseodymium is a lanthanide that has a grey white shiny color in its natural solid state. It has some resistance to corrosion, but it will form a green oxide coating if exposed to air. Praseodymium has an atomic number of 140.90765, a melting point of 1715 °F, and a boiling point of 6368 °F. Some common uses of praseodymium include: as a component in cubic-zirconium, as a component in alloys, as the core of carbon arc lights, as an ingredient in glasses and enamels to give a yellow color, and as an alloy with nickel to produce magneto caloric effects.

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Isolation

Praseodymium occurs in rare earth minerals such as monazite and bastnasite along with other lanthanides. Extraction processes can be used to isolate praseodymium from these minerals.

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The similarity of lanthanide chemical characteristics makes it difficult to separate them from the minerals in which they occur together. The isolation of praseodymium from these minerals is a highly complex multi-step process; due to the complexity of praseodymium separation, it is never performed on a small laboratory scale basis. Some of the processes that are needed to separate praseodymium include solvent extraction and ion exchange chromatography.

The first step to praseodymium isolation involves separating the lanthanides from the mineral in their salt forms by treating the mineral ore with sulphuric acid, hydrochloric acid, and sodium hydroxide. Using the extraction techniques, praseodymium is reduced to praseodymium fluoride. The isolation of praseodymium from fluoride occurs by a heated reaction with fluoride. Additional isolation procedures using a vacuum take out any small calcium contaminants that did not react with the fluoride to yield pure praseodymium. Pure praseodymium is slightly toxic and needs to be handled with care.


General
Name Praseodymium
Symbol Pr
Number 59
Chemical series lanthanides
Group n/a
Period 6
Block f
Appearance grayish white
Standard atomic weight 140.90765(2)  g·mol−1
Electron configuration [Xe] 4f3 6s2
Electrons per shell 2, 8, 18, 21, 8, 2
Atomic properties
Crystal structure hexagonal
Oxidation states 3 (mildly basic oxide)
Electronegativity 1.13 (scale Pauling)
Ionization energies 1st:  527  kJ·mol−1
(more) 2nd:  1020  kJ·mol−1
(more) 3rd:  2086  kJ·mol−1
Atomic radius 185 pm
Atomic radius (calc.) 247  pm
Covalent radius
Van der Waals radius
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 1208 K (935 °C, 1715 °F)
Boiling point 3793 K (3520 °C, 6368 °F)
Critical point
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
Miscellaneous
Magnetic ordering
Electrical resistivity (r.t.) (α, poly) 0.700 µΩ·m
Thermal conductivity (300 K) 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
Mohs hardness
Vickers hardness 400  MPa
Brinell hardness 481  MPa
CAS registry number 7440-10-0

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