| 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 |