Pa
231.040Protactinium
Protaktinyum
Protactinium is a rare radioactive actinide with atomic number 91. It is known for protactinium-231, uranium decay chains, Pa-231/Th-230 marine sediment dating and fundamental actinide chemistry.
91
231.04 g/mol
[Rn] 5f² 6d¹ 7s²
2 | 8 | 18 | 32 | 20 | 9 | 2
1.5
15.37 g/cm³
1567.8 °C
4026.8 °C
Kasimir Fajans
The longer-lived isotope protactinium-231 was discovered in uranium minerals in 1917-1918 by Lise Meitner and Otto Hahn, with related independent work by Frederick Soddy, John Cranston and Alexander Fleck. The name means parent of actinium because Pa-231 decays toward actinium-227.
Protactinium-231
Half-life: About 32,760 years. Longest-lived natural protactinium isotope in the uranium-235 decay series.Protactinium-234
Half-life: About 6.7 hours. Short-lived uranium-series isotope important in decay-chain studies.Pa₂O₅
Protactinium(V) OxideResearch compound for protactinium chemistry.PaCl₅
Protactinium(V) ChlorideResearch precursor for protactinium halide chemistry.PaF₅
Protactinium(V) FluorideActinide fluoride chemistry research.- Pa-231/Th-230 isotope ratios in marine sediment and carbonate dating research
- Tracer studies of ocean circulation and particle scavenging
- Fundamental actinide chemistry and 5f-electron behavior research
- Nuclear data studies connected to uranium decay chains
Protactinium has no biological role. All protactinium isotopes are radioactive, and Pa-231 is radiotoxic because it emits alpha radiation and has a long half-life.
- Protactinium is one of the rarest naturally occurring actinides in Earth’s crust.
- Pa-231/Th-230 ratios help reconstruct past ocean processes and sedimentation history.
- Protactinium sits between thorium and uranium, making it a useful case for studying early actinide chemistry.
- Protactinium has atomic number 91 and symbol Pa.
- Its electron configuration is [Rn] 5f² 6d¹ 7s².
- The +5 oxidation state is especially important.
- Remember Pa-231 for uranium-series decay and marine sediment dating.
What is the atomic number of protactinium?
The atomic number of protactinium is 91.
What is the electron configuration of protactinium?
Protactinium has the electron configuration [Rn] 5f² 6d¹ 7s².
What is protactinium used for?
Protactinium has no broad commercial use; it is used mainly in geochronology, ocean-tracer and actinide chemistry research.
What is protactinium-231?
Protactinium-231 is a long-lived alpha-emitting isotope in the uranium-235 decay series with a half-life of about 32,760 years.
Why is protactinium rare?
Protactinium is produced only in trace amounts in natural radioactive decay chains, so macroscopic quantities are uncommon.