Praseodymium (Pr)
Praseodymium (Pr) is a lanthanide with atomic number 59 and a standard atomic weight of 140.91. At room temperature it is a solid that melts at 931 °C and boils at 3,520 °C.
Praseodymium key facts
Praseodymium at a glance
Identity
| Symbol | Pr |
|---|---|
| Atomic number (Z) | 59 |
| Atomic weight | 140.91 ± 0.01 (CIAAW 2024) |
| Category | Lanthanide |
| Group | — (f-block: lanthanide series) |
| Period | 6 |
| Block | f-block |
| CAS number | 7440-10-0 |
Atomic properties
| Electron configuration | [Xe] 4f3 6s2 Full: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f3 5s2 5p6 6s2 |
|---|---|
| Electrons per shell | 2, 8, 18, 21, 8, 2 |
| Oxidation states | +3 Less common: 0, +1, +2, +4, +5 |
| Electronegativity (Pauling) | 1.13 |
| First ionisation energy | 5.47 eV (527.8 kJ/mol) 2nd: 10.631 eV · 3rd: 21.624 eV |
| Electron affinity | 0.962 eV |
| Atomic radius (empirical) | 185 pm |
| Covalent radius | 176 pm |
| Van der Waals radius | 240 pm |
Physical properties
| State at 25 °C | Solid |
|---|---|
| Melting point | 931 °C · 1,707.8 °F · 1,204.15 K |
| Boiling point | 3,520 °C · 6,368 °F · 3,793.15 K |
| Density | 6.773 g/cm³ |
| Specific heat capacity | 0.193 J/(g·K) |
| Thermal conductivity | 12.5 W/(m·K) |
| Crystal structure | Hexagonal |
Isotopes & abundance
| Natural occurrence | Primordial |
|---|---|
| Radioactive | No |
| Natural isotopes (abundance) | 141Pr 100% |
| Stable isotopes | 1 |
| Known isotopes | 41 |
| Abundance in Earth's crust | 9.2 mg/kg |
| Abundance in seawater | 0.00000064 mg/L |
Atomic weights: CIAAW Abridged Standard Atomic Weights 2024. Other properties: standard reference compilations, checked October 2026; predicted values are marked.
Praseodymium electron configuration
Praseodymium has 59 electrons. Written in short form, its ground-state configuration is [Xe] 4f3 6s2 — the electrons of the noble gas xenon, plus 4f3 6s2.Written out in full: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f3 5s2 5p6 6s2.
Discovery and name
1885 — Carl Auer von Welsbach · Austria.
Greek prasios didymos, green twin.
Known for
Used with neodymium in magnets, in aircraft-engine alloys and in welders' goggles (didymium glass).
Isotopes of praseodymium
Naturally occurring praseodymium is a mix of 1 isotope. Each has 59 protons; they differ in the number of neutrons:
| Isotope | Protons | Neutrons | Natural abundance | Stability |
|---|---|---|---|---|
| 141Pr | 59 | 82 | 100% | stable |
41 isotopes of praseodymium are known in our data set (half-lives as published in nuclear data tables).
Praseodymium and its neighbours in the lanthanide series
Neighbouring elements in the same f-block series:
| Element | Z | Atomic weight | Melting point | Boiling point | Density | Electronegativity |
|---|---|---|---|---|---|---|
| Lanthanum | 57 | 138.91 | 920 °C | 3,464 °C | 6.15 g/cm³ | 1.1 |
| Cerium | 58 | 140.12 | 799 °C | 3,443 °C | 6.77 g/cm³ | 1.12 |
| Praseodymium | 59 | 140.91 | 931 °C | 3,520 °C | 6.773 g/cm³ | 1.13 |
| Neodymium | 60 | 144.24 | 1,016 °C | 3,074 °C | 7.01 g/cm³ | 1.14 |
| Promethium | 61 | [145] | 1,042 °C | 3,000 °C | 7.26 g/cm³ | 1.13 |
| Samarium | 62 | 150.36 | 1,072 °C | 1,794 °C | 7.52 g/cm³ | 1.17 |