Periodic TableEinsteinium (Es)
Einsteinium is an actinide with atomic number 99, in period 7, in the f-block of the periodic table. Its atomic mass is 252 u and its electron configuration is [Rn] 5f¹¹ 7s². Solid at 25 °C.
Key facts
| Atomic number | 99 |
|---|---|
| Atomic mass | 252 u |
| Category | Actinide |
| Period | 7 |
| Group | f-block, no group number |
| Block | f |
| Electron configuration | [Rn] 5f¹¹ 7s² |
| Electrons per shell | 2, 8, 18, 32, 29, 8, 2 |
| Electronegativity (Pauling) | 1.3 |
| Oxidation states | +2, +3, +4common in bold |
| State at 25 °C | Solid |
| Melting point | 1133 K859.85 °C |
| Boiling point | 1269 K995.85 °C |
| Density | 8.84 g/cm³ |
Atomic properties
| First ionization energy | 6.42 eV |
|---|---|
| Electron affinity | --- |
| Atomic radius | --- |
| Covalent radius | --- |
| Van der Waals radius | 245 pm |
| Common ions | Es³⁺ |
| Protons, neutrons, electrons | 99, 153, 99 |
Physical and thermal properties
| Molar volume | 28.52 cm³/mol |
|---|---|
| Heat of fusion | --- |
| Heat of vaporization | --- |
| Specific heat | --- |
| Thermal conductivity | --- |
| Thermal expansion | --- |
| Mohs hardness | --- |
| Young’s modulus | --- |
| Crystal structure | Face-centered cubic |
| Magnetic type | Paramagnetic |
Identification and history
| CAS number | 7429-92-7 |
|---|---|
| Latin name | Einsteinium |
| Discovered by | L. Berkeley National Laboratory · 1952 |
| Named by | --- |
Natural isotopes
Einsteinium has no stable isotopes: every isotope is radioactive.
Data checked against PubChem (NIH), IUPAC, the NIST Atomic Spectra Database and the IAEA (NUBASE and AME), the same data you see in the app.
A dash (---) means there is no reliable published measurement. The app never makes one up.
See Einsteinium in the app
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