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Einsteinium (Es)
Atomic number 99 · Actinide
| Atomic number | 99 |
|---|---|
| Atomic mass | 252.0 u |
| Molar mass | 252.0 g/mol |
| Category | Actinide |
| Group / period / block | — / 7 / f |
| Electron configuration | [Rn] 5f11 7s2 |
| Electrons per shell | 2, 8, 18, 32, 29, 8, 2 |
| Density | 8.84 g/cm³ |
| First ionisation energy | 6.3684 eV |
| Melting point | 1133.15 K (860.00 °C) |
| Common oxidation states | +3 |
Uses
Research only — synthetic, made a few atoms at a time
Discovery
1952, Argonne, Los Alamos, U of Calif