Atomic number 91 · actinide · Atomic mass 231.04 u
| Atomic Number | 91 |
| Atomic Mass | 231.0400 u |
| Category | actinide / 锕系元素 |
| Group | — |
| Period | 7 |
| Block | F |
| Electron Configuration | [Rn] 5f² 6d¹ 7s² |
| Electronegativity (Pauling) | 1.5 |
| Phase at STP | Solid |
| Density | 15.37 g/cm³ |
| Year Discovered | 1913 |
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