Praseodymium
Atomic Data
| Atomic Number | 59 |
| Symbol | Pr |
| Atomic Weight | 140.91 u |
| Density (STP) | 6.77 g/cm³ |
| Melting Point | 934.85 °C (1208 K) |
| Boiling Point | 3519.85 °C (3793 K) |
| Electronegativity | 1.13 (Pauling) |
| Electron Config. | 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f3 5s2 5p6 6s2 |
| Oxidation States | +3, +4 |
| Phase at STP | Solid |
| Category | Lanthanoid |
| Period / Group | 6 / None |
| CAS Number | 7440-10-0 |
Electron Configuration
[Xe] 4f3 6s2
| Shell | n | Subshell | Electrons | Cumulative |
|---|---|---|---|---|
| K | 1 | 1s | 2 | 2 |
| L | 2 | 2s | 2 | 4 |
| L | 2 | 2p | 6 | 10 |
| M | 3 | 3s | 2 | 12 |
| M | 3 | 3p | 6 | 18 |
| M | 3 | 3d | 10 | 28 |
| N | 4 | 4s | 2 | 30 |
| N | 4 | 4p | 6 | 36 |
| N | 4 | 4d | 10 | 46 |
| N | 4 | 4f | 3 | 49 |
| O | 5 | 5s | 2 | 51 |
| O | 5 | 5p | 6 | 57 |
| P | 6 | 6s | 2 | 59 |
| Total | 59 | 59 | ||
Isotopes of Praseodymium
Praseodymium is monoisotopic: ¹⁴¹Pr is its only naturally occurring stable isotope, accounting for 100% of all natural Praseodymium.
| Isotope | Symbol | Protons | Neutrons | Abundance | Stability |
|---|---|---|---|---|---|
| Praseodymium-141 | ¹⁴¹Pr | 59 | 82 | 100 | Stable |
Abundance & Occurrence
Praseodymium is present in Earth's crust at approximately 9.2 ppm by mass and at approximately 0.9 ppm by mass throughout the universe.
Earth's Crust (ppm by mass)
Universe (ppm by mass)
Discovery & History
Read more about the discovery of the periodic table of elements →
Safety & Handling
- Dust and fume inhalation: Praseodymium metal dust and oxide are respiratory irritants; as with all lanthanides, fine particulate inhalation should be avoided with appropriate dust controls and respiratory protection.
- Fire hazard: Praseodymium metal is flammable in powdered form; use Class D agents for metal fires and avoid contact with water.
- Skin and eye contact: Praseodymium chloride and other soluble salts are mild irritants to skin and eyes; wear appropriate PPE when handling solutions or powders.
- General precautions: Praseodymium has low acute systemic toxicity; the principal hazard category is occupational dust/fume inhalation during processing and manufacturing.
Praseodymium in the Real World
Real-World Uses
- Nd-Fe-B magnet additive: Substituting praseodymium for neodymium in (Nd,Pr)-Fe-B magnets reduces cost while maintaining high magnetic performance; most commercial NdFeB magnets contain a significant fraction of praseodymium.
- Protective eyewear for welding: Didymium glass (a mixture of praseodymium and neodymium oxides) absorbs the intense sodium yellow D-lines (589 nm) produced in glass-blowing and welding flames, protecting workers' eyes without excessive darkening of the field of view.
- High-temperature magnet performance: Praseodymium additions improve the coercivity and maximum operating temperature of permanent magnets used in electric vehicle motors and wind turbine generators.
- Fibre-optic amplifiers: Praseodymium-doped fluoride fibre amplifiers (PDFAs) amplify signals in the 1300 nm wavelength window used in some optical fibre networks.
- Glass and ceramic colouring: Praseodymium oxide produces a distinctive yellow-green colour in glass, glazes, and ceramic pigments; praseodymium yellow is a thermally stable pigment used in coloured sanitaryware and tableware.
Downloadable Resources
Free periodic table reference sheets for classrooms, study sessions, and laboratory use.
Frequently Asked Questions
What is praseodymium used for?
Praseodymium is used in high-strength permanent magnets: it is a component of neodymium-iron-boron (NdFeB) magnets, where it is often used as a partial substitute for neodymium. These magnets are used in electric vehicle motors and wind turbine generators. Praseodymium oxide produces a distinctive bright yellow-green colour in ceramics and glass. Didymium glass containing praseodymium is used in safety goggles for glassblowers and welders.
Is praseodymium toxic?
Praseodymium and its compounds are considered to have low to moderate toxicity. They are mildly irritating to skin and eyes, and praseodymium dust should not be inhaled. The element has no known biological role. Like other rare-earth elements, praseodymium is generally handled with standard precautions for fine metal dusts.
How was praseodymium discovered?
Praseodymium was discovered in 1885 by Austrian chemist Carl Auer von Welsbach. He separated the mixture known as 'didymium' (previously thought to be an element) into two distinct components by fractional crystallisation: praseodymium (green salts) and neodymium (pink salts). The name praseodymium comes from the Greek 'prasios didymos', meaning green twin, reflecting the green colour of its salts.
Why is praseodymium used in safety goggles?
Didymium glass: a mixture of praseodymium and neodymium oxides in glass: absorbs the intense yellow-orange sodium D-line emission at 589 nm, which is produced in large quantities when glass or metal is worked at high temperatures. Without filtering, this intense yellow light causes eye strain and can mask dangerous infrared radiation. Didymium goggles protect glassblowers and scientific glassblowers from this hazard while allowing a clear view of the work.