Element 99
Einsteinium
Actinides
Einsteinium (Es) is in the f-block of the periodic table — group 3, period 7.
Einsteinium is a synthetic element with symbol Es and atomic number 99.
Key data
- Atomic number
- 99
- Atomic mass
- 252.000 u
- Group / Period
- 3 / 7
- Block
- f-block
- Phase at STP
- Solid
- Density
- 8.84 g/cm³
- Melting point
- 859.9 °C
- Boiling point
- 995.9 °C
- Electron configuration
- [Rn] 5f11 7s2
Periodic table block
Einsteinium is in the f-block (group 3, period 7). Elements land in the f-block when their highest-energy electrons fill an f subshell — these are the lanthanides and actinides shown beneath the main table.
New to this? Periodic table blocks explained: s, p, d, and f
Common uses
- •Research only
- •Extremely rare
- •Synthesized in 1952 H-bomb test
Discovery
Year: 1952
Discovered by: Lawrence Berkeley National Laboratory
Frequently asked questions
What is the atomic number of Einsteinium?
Einsteinium has atomic number 99. Its symbol is Es and its atomic mass is 252 u.
What category of element is Einsteinium?
Einsteinium is classified as actinides. It sits in group 3, period 7 of the periodic table.
What block of the periodic table is Einsteinium in?
Einsteinium is in the f-block (group 3, period 7). Its highest-energy electrons occupy the f subshell — you can see this in its electron configuration, [Rn] 5f11 7s2.
What is Einsteinium used for?
Common uses of Einsteinium include: Research only, Extremely rare, Synthesized in 1952 H-bomb test.
When was Einsteinium discovered?
Einsteinium was discovered in 1952 by Lawrence Berkeley National Laboratory.
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