91Pa

Protactinium

Actinide

Protactinium (Pa) is element 91, an actinide, in period 7 of the periodic table. Its standard atomic weight is 231.036, it melts at 1572 °C and boils at 4000 °C. Discovered by Kasimir Fajans, 1913.

Atomic Number91

SymbolPa

NameProtactinium

Atomic Weight231.036 u

CategoryActinide

Period7

Melting Point1572 °C

Boiling Point4000 °C

Density15.37 g/cm³

Electron Config[Rn] 5f2 6d1 7s2

Discovered ByKasimir Fajans, 1913

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