Praseodymium
Element 59 · Lanthanide
Praseodymium is a typical lanthanide: silvery, malleable, quick to tarnish, and almost always +3 in its compounds. For decades it hid inside a supposed element called didymium until chemists separated it from its ‘twin,’ neodymium, in 1885 — its name literally means ‘green twin’ for the color of its salts.
Today its main value is in materials: small additions of praseodymium make magnesium alloys strong enough for aircraft parts, and it joins neodymium in the permanent magnets of motors and headphones. Didymium glass containing praseodymium still shields glassblowers' and welders' eyes.
Key facts
| Atomic number | 59 |
|---|---|
| Atomic weight | 140.91 |
| Category | Lanthanide |
| Group / Period | — / 6 |
| Block | f |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f3 |
| Common oxidation states | +3, +4 |
| State at STP | Solid |
| Electronegativity | 1.13 |
| Density | 6.77 g/cm³ |
| Melting point | 931 °C |
| Boiling point | 3520 °C |
Occurrence
Praseodymium occurs in monazite and bastnasite alongside the other light lanthanides, and is separated from them by solvent extraction or ion exchange.
Applications
High-strength magnesium alloys for aircraft
Permanent magnets (with neodymium)
Didymium glass for welders' goggles
Carbon arc lights (historic)
Common compounds
- praseodymium oxide
- praseodymium chloride
- praseodymium fluoride
Its name means ‘green twin’ — praseodymium and neodymium were once thought to be a single element called didymium until they were separated in 1885.
Data source: IUPAC standard atomic weights 2021