Atomic number 87 · alkali metal · Atomic mass 223 u
| Atomic Number | 87 |
| Atomic Mass | 223.0000 u |
| Category | alkali metal / 碱金属 |
| Group | 1 |
| Period | 7 |
| Block | S |
| Electron Configuration | [Rn] 7s¹ |
| Electronegativity (Pauling) | 0.7 |
| Phase at STP | Solid |
| Density | 2.48 g/cm³ |
| Year Discovered | 1939 |
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