Element Protactinium

Protactinium ElementProtactinium (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

IsotopeMass/DaNatural abundance (atom %)Nuclear spin (I)Magnetic moment (μ/μN)
231Pa1003/2

Radiosotope data

IsotopeMass/DaHalf-lifeMode of decayNuclear spinNuclear magnetic moment
228Pa228.0310022 hEC to 228Th; α to 224Ac33.5
229Pa229.032091.5 dEC to 229Th; α to 225Ac5/2
230Pa230.0345317.4 dEC to 230Th; α to 226Ac; β to 230U22.0
231Pa231.035880 (3)32500 yα to 226Ac; SF3/22.01
232Pa232.038581.31 dEC to 232Th; β to 232U2
233Pa233.0402427.0 dβ to 233U3/24.0
234Pa234.043306.69 hβ to 234U4

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