Element Protactinium
Protactinium (formerly protoactinium) is a chemical element with the symbol Pa and atomic number 91.
Protactinium was first identified in 1913 by Kasimir Fajans and Oswald Helmuth Göhring and named brevium because of the short half-life of the specific isotope studied, i.e. protactinium-234.
It is a dense, silvery-gray actinide metal which readily reacts with oxygen, water vapor and inorganic acids.
It forms various chemical compounds in which protactinium is usually present in the oxidation state +5, but it can also assume +4 and even +3 or +2 states.
Names and Identifiers
| Chemical Formula: | Pa |
| CAS: | 7440-13-3 |
| Molecular Weight: | 231.03600 g/mol |
| EC Number : | n/a |
| MDL Number: | n/a |
| Color: | silvery-white |
| Other Names: | Protoattinio, Protaktinium |
| PubChem CID: | 23945 |
| IUPAC Name: | Protactinium |
| Inchl: | InChI=1S/Pa |
| InChI Key: | XLROVYAPLOFLNU-UHFFFAOYSA-N |
| Canonical SMILES: | [Pa] |
| ICSC Number: | n/a |
Physical & Chemical Properties
| Phase: | Solid |
| Density: | 15.37 g/cm³ |
| Boiling Point: | 4300 K (4027 °C, 7280 °F) |
| Melting Point: | 1841 K (1568 °C, 2854 °F) |
| Molecular Formula: | Pa |
| Flash Point: | n/a |
| Exact Mass: | 231.03600 |
Twenty-nine radioisotopes of protactinium have been discovered, the most stable being 231Pa with a half-life of 32,760 years, 233Pa with a half-life of 27 days, and 230Pa with a half-life of 17.4 days
Naturally occurring isotopes
| Isotope | Mass/Da | Natural abundance (atom %) | Nuclear spin (I) | Magnetic moment (μ/μN) |
|---|---|---|---|---|
| 231Pa | 100 | 3/2 |
Radiosotope data
| Isotope | Mass/Da | Half-life | Mode of decay | Nuclear spin | Nuclear magnetic moment |
|---|---|---|---|---|---|
| 228Pa | 228.03100 | 22 h | EC to 228Th; α to 224Ac | 3 | 3.5 |
| 229Pa | 229.03209 | 1.5 d | EC to 229Th; α to 225Ac | 5/2 | |
| 230Pa | 230.03453 | 17.4 d | EC to 230Th; α to 226Ac; β– to 230U | 2 | 2.0 |
| 231Pa | 231.035880 (3) | 32500 y | α to 226Ac; SF | 3/2 | 2.01 |
| 232Pa | 232.03858 | 1.31 d | EC to 232Th; β– to 232U | 2 | |
| 233Pa | 233.04024 | 27.0 d | β– to 233U | 3/2 | 4.0 |
| 234Pa | 234.04330 | 6.69 h | β– to 234U | 4 |