Protactinium

Atomic number

91

Atomic mass (u)

231.03588

Category

Actinide

Standard state

Solid

Melting point

1571.85 °C (1845 K)

Boiling point

Not reported

Density (g/cm³)

15.37

Electronegativity (Pauling)

1.5

Electron configuration

[Rn]7s2 5f2 6d1

Oxidation states

+5, +4

Atomic radius (pm)

243

First ionization energy (eV)

5.89

Discovery & recognition

Discovery year / period (PubChem)

1913

Discovery credited to (RSC)

Kasimir Fajans and Otto Göhring

Date or period recorded by RSC

1913

Discovery place

Berlin, Germany (long-lived isotope, 1918); earlier identification was a different isotope

An ancient date does not identify a first human discovery. Different references may date observation, isolation and formal recognition differently.

Natural occurrence & production

The creation of an element’s nuclei and its concentration into terrestrial deposits are different processes. The occurrence note below concerns its presence or production on Earth; it is not a complete account of nucleosynthesis.

“Small amounts of protactinium are found naturally in uranium ores.”

Royal Society of Chemistry · occurrence excerpt ↗

Continue the research

Reference values are not product specifications. Blank values have not been estimated. For superheavy elements, some properties and family assignments are theoretical or incompletely measured.