Protactinium has a bright metallic lustre which it retains for some time in air. The element is superconductive below 1.4 K. The element is a dangerous toxic material and requires precautions similar to those used when handling plutonium. Protactinium is one of the rarest and most expensive naturally occurring elements. The element is an α-emitter and is a radiological hazard similar to polonium. Protactinium is a highly toxic and radioactive rare earth metal that requires special handling. It is found in pitchblende and ores form Zaire and is one of the rarest and most expensive naturally occurring elements.
This sample of uraninite contains some about 10-6 grammes of actinium at any one time. Image adapted with permission fromProf James Marshall's (U. North Texas, USA)Walking Tour of the elements CD.
Binary compounds with halogens (known as halides), oxygen (known as oxides), hydrogen (known as hydrides), and other compounds of protactinium where known.
Protactinium wasdiscovered by Otto Hahn, Lise Meitner, Frederick Soddy, John Cranston in 1913 at Germany, England.Origin of name: from the Greek word "protos" meaning "first".
Density of solid: 15370 kg m-3
Molar volume: 15.18 cm3
Thermal conductivity: 47 (estimate) W m‑1 K‑1
Melting point: 1841 [1568 °C (2854 °F)] K
Boiling point: 4300 [ca. 4000 °C (7232 °F)] K
Enthalpy of fusion: 20.5 kJ mol-1
Atomic radius (empirical): 180 pm
Molecular single bond covalent radius: 169 (coordination number 5) ppm
van der Waals radius: [ 340 ] ppm
Pauling electronegativity: 1.5 (Pauling units)
Allred Rochow electronegativity: 1.14 (Pauling units)
Mulliken-Jaffe electronegativity: (no data)
First ionisation energy: 568 kJ mol‑1
Second ionisation energy: 1150 kJ mol‑1
Third ionisation energy: 1790 kJ mol‑1
Universe: (no data) ppb by weight
Crustal rocks: 0.000010 ppb by weight
Human: (no data) ppb by weight
