Atomic number:91

Group numbers:3

Period:7

Electronic configuration:[Rn] 5f² 6d¹ 7s²

Formal oxidation number:+4 +5

Electronegativities:1.5

Atomic radius / pm:156.1

Relative atomic mass:231.03588 ± 0.00002

 

Protactinium was discovered by Kasimir Fajans and Otto H. Göhring (DE) in 1913. The origin of the name comes from the Greek word protos meaning first. It is a very rare, silvery-white, extremely radioactive metal that resists alkalis, reacts with oxygen, acids and steam. Protactinium is highly radiotoxic, extremely toxic and must be handled with great care. Protactinium does not occur in nature. It is found among fission products of uranium, thorium and plutonium.

Density / g dm^-3:15370 (calc.)

Molar volume / cm³mol^-1:15.03 (calc.)

Electrical resistivity / μΩcm:19.1 (20 °C)

Thermal conductivity / W m^-1K^-1:47

Melting point / °C:1572

Boiling point / °C:-

Heat of fusion / kJ mol^-1:16.7

Heat of vaporization / kJ mol^-1:481

Heat of atomization / kJ mol^-1:607

1st ionization energy / kJ mol^-1:568.30

2nd ionization energy / kJ mol^-1:-

3rd ionization energy / kJ mol^-1:-

in the atmosphere / ppm:-

in the Earth's crust / ppm:2E-12

in the oceans / ppm:-