Einsteinium - Es
Einsteinium (Es)
Einsteinium is a radioactive actinide produced in very small quantities. It does not have a standard atomic weight; the bracketed value below identifies a representative isotope mass number.
| Atomic number | 99 |
|---|---|
| Representative isotope mass number | [252] |
| Electron configuration | [Rn] 5f11 7s2 |
| Density | not established |
| Melting point | 860 °C |
| Boiling point | not established |

Uses and applications
Einsteinium has no established applications outside research. Only tiny amounts are produced, so experiments focus on its chemistry, nuclear properties, and the formation of heavier elements.
Einsteinium and water management
Einsteinium is not used in water treatment. Any possible presence in laboratory or nuclear-related liquid waste requires isotope-specific analysis and radiological waste controls.
Occurrence and environmental context
Einsteinium is a synthetic actinide with no stable isotopes. Its occurrence outside controlled production is extremely limited. Environmental assessment, if relevant, depends on isotope, activity, chemical form, and the specific source.
Health and safety
Einsteinium requires specialised radiological controls. Exposure risk depends on isotope, activity, chemical form, and exposure route. Follow applicable radiation-protection procedures and institutional requirements when handling radioactive materials or waste.
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Sources and further reading
Element page last reviewed: 24 October 2026 by Lenntech.