Praseodymium
[Xe] 4f³ 6s² · 2 · 8 · 18 · 21 · 8 · 2
A lanthanide whose salts take a distinctive green — hence the name, green twin. Praseodymium goes into the strongest permanent magnets and into glassblowers' safety glasses.
3D model
Bohr model: nucleus and electron shells from the real configuration. Valence electrons are highlighted.
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Atomic properties
- Atomic number
- 59
- Atomic mass
- 140.908 а.е.м.
- Electron configuration
- [Xe] 4f³ 6s²
- Electrons per shell
- 2 · 8 · 18 · 21 · 8 · 2
- Block
- f-block
- Group
- no data
- Period
- 6
- Electronegativity (Pauling)
- 1.13
- Electronegativity (Allen)
- 1.09
- Atomic radius
- 239 pm
- Covalent radius
- 203 pm
- Van der Waals radius
- 239 pm
- Ionisation energy 1
- 527 kJ/mol
- Ionisation energy 2
- 1 020 kJ/mol
- Ionisation energy 3
- 2 086 kJ/mol
- Ionisation energy 4
- 3 761 kJ/mol
- Ionisation energy 5
- 5 551 kJ/mol
- Electron affinity
- 50 kJ/mol
- Common oxidation states
- +3
- Oxidation states
- +2, +3, +4, +5
Physical properties
- State at 25 °C
- solid
- Density
- 6.77 g/cm³
- Melting point
- 1 208 K · 934.9 °C
- Boiling point
- 3 403 K · 3 129.9 °C
- Speed of sound
- 2 280 m/s
Thermal properties
- Heat of fusion
- 6.89 kJ/mol
- Heat of vaporisation
- 331 kJ/mol
- Specific heat capacity
- 0.193 J/(g·K)
- Thermal conductivity
- 12.5 W/(m·K)
Mechanical properties
- Young's modulus
- 37.3 GPa
- Shear modulus
- 14.8 GPa
- Bulk modulus
- 28.8 GPa
- Poisson ratio
- 0.28
- Mohs hardness
- no data
- Brinell hardness
- 481 MPa
Electrical and magnetic properties
- Electrical resistivity
- 700 nΩ·m
- Magnetic ordering
- paramagnetic
- Curie point
- no data
- Néel point
- no data
- Superconducting point
- no data
Crystal structure
- Crystal structure
- hexagonal close-packed (hcp)
- Lattice constants
- a = 367.21 pm · c = 1 183.26 pm
Abundance
- In the crust
- 9.2 mg/kg
- In the ocean
- 6.4·10⁻⁷ mg/L
- In the universe
- 0.2 mg/kg
- In the human body
- no data
Isotopes
| Isotope | Abundance | Half-life | Decay mode |
|---|---|---|---|
| 141Pr | 100 % | stable | — |
Praseodymium-141 is the only stable isotope. Praseodymium-143 is a short-lived fission product.
Discovery
- Year of discovery
- 1885
- Discovered by
- Carl Auer von Welsbach
- Where
- Austria
- Origin of the name
- from Greek prasios didymos (green twin): its salts are green
History
Mosander isolated didymium from lanthanum in 1841, believing it an element. Forty-four years later Auer von Welsbach split didymium into two: green praseodymium and the new neodymium.
Where it occurs
9.2 mg/kg of the crust. It travels with the other light lanthanides in bastnäsite and monazite.
How it is produced
By separating rare-earth concentrates; more often praseodymium is not separated from neodymium at all, and the didymium mixture goes straight into magnets.
Role in living things
No biological role.
Safety
Of low toxicity. The powdered metal is pyrophoric.
Uses
- Neodymium-iron-boron permanent magnets, where praseodymium partly replaces neodymium
- Didymium glass in welders' and glassblowers' goggles: it absorbs the yellow sodium emission
- Yellow ceramic pigments
- Alloying magnesium for aerospace
- Refrigeration to ultra-low temperatures by adiabatic demagnetisation
Curiosities
- The name means green twin, from the colour of its salts and its origin in didymium.
- Glassblowers wear didymium goggles to see the shape of the work through the blinding sodium glare.
- Praseodymium and neodymium were taken for one element for forty-four years.
- Praseodymium-nickel alloy shows one of the strongest magnetocaloric effects and is used to reach ultra-low temperatures.