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Protactinium
Element 91 · 231.03588 u
Protactinium is one of the rarest and most expensive naturally occurring elements.
Physical Properties
| Atomic Mass | 231.03588 u |
| Density | 15.37 g/cm³ |
| Melting Point | 1841.0 K |
| Boiling Point | 4300.0 K |
| Appearance | Silvery metallic, bright luster |
| State at Room Temp | Solid |
Chemical Properties
| Electronegativity | 1.5 (Pauling) |
| 1st Ionization Energy | 568.0 kJ/mol |
| Electron Affinity | 53.03 kJ/mol |
| Oxidation States | +3, +4, +5 |
Atomic Properties
| Electron Configuration | [Rn] 5f2 6d1 7s2 |
| Atomic Radius | 163.0 pm |
| Van der Waals Radius | 243.0 pm |
Discovery
| Discovered By | Kasimir Fajans, Oswald Helmuth Gohring |
| Discovery Year | 1913 |
| Location | Karlsruhe, Germany |
| Named After | Greek 'protos' and 'actinium' meaning parent of actinium |
About Protactinium
Protactinium is a dense, silvery-gray radioactive actinide. It produces actinium-227 through decay. It is both toxic and highly radioactive, costing around $280,000 per gram.
Uses & Applications
Scientific research, particularly geochronology (ocean sediment dating).
Fun Fact
Protactinium costs around $280,000 per gram, making it one of the most expensive naturally occurring elements.
Isotopes
| Mass Number | Abundance | Half-Life | Stable |
| 231 | 1.0% | 32,760 years | No |
Electron Configuration
[Rn] 5f2 6d1 7s2