Name protactinium
Symbol Pa
Atomic Weight 231.03588
Atomic Number 91
CAS ID 7440-13-3
Group Number
Group Name Actinoid
Period Number 7
Origin of Name Greek, protos = "first."
Year Discovered 1917
Discovery Credits Discovered by Otto Hahn and Lise Meitner at Berlin, by K. Fajans at Karlsruhe, Germany, and by F. Soddy, J. A. Cranston, and A. Fleck at Glasgow, Scotland.
Class Metallic
Color Silvery Metallic
Standard State Solid at 77 F & 298 K
Description Radioactive, silvery metal found naturally in uranium ores. Attacked by oxygen, steam, and acids, but not by alkalis. Little used. Primarily occurs as a trace amount (a few ppm) in uranium minerals where it is a decay product of uranium

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