Einsteinium (Es): Electron Configuration, Properties and Uses
Einsteinium (Es): Electron Configuration, Properties and Uses
Electron configuration [Rn] 7s2 5f11 · f-block, actinide series · period 7 · Ar [252]
Einsteinium data
- Atomic number
- 99
- Relative atomic mass
- [252]
- Group
- – (actinide series)
- Period
- 7
- Block
- f
- Category
- Actinide
- Electron configuration
- [Rn] 7s2 5f11
- Full configuration
- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f11
- Electrons per shell
- 2, 8, 18, 32, 29, 8, 2 (K L M N O P Q)
- Valence electrons
- 2 (in the outer shell)
- Electronegativity (Pauling)
- 1.3
- First ionisation energy
- 6.42 eV
- Atomic radius (van der Waals)
- 245 pm
- State at room temperature
- Solid
- Melting point
- 860 °C
- Boiling point
- no data
- Density
- no data
- Common oxidation states
- +3
- Discovered
- 1952
Source: PubChem (NIH, accessed 13 Nov 2026); atomic mass: IUPAC standard atomic weight.
Electron shell diagram
K 2 · L 8 · M 18 · N 32 · O 29 · P 8 · Q 2
Orbital diagram (outer electrons)
About einsteinium
Einsteinium is a chemical element with the symbol Es and atomic number 99. It belongs to the actinide series in period 7 (f-block), usually shown below the main table. The element was discovered in 1952. It is named after Albert Einstein. Einsteinium is a solid at room temperature, melting at 860 °C.
Einsteinium electron configuration
The electron configuration of einsteinium is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f11, or in short [Rn] 7s2 5f11. Its electrons occupy 7 shells: K = 2, L = 8, M = 18, N = 32, O = 29, P = 8, Q = 2. As an actinide, einsteinium fills the 5f subshell. Its outer 7s subshell holds 2 electrons; valence electrons for this series are not assigned by the usual group rule. When it forms cations, electrons leave the outermost subshell first: Es3+ = [Rn] 5f10.
Filling order: 1s2(2) → 2s2(4) → 2p6(10) → 3s2(12) → 3p6(18) → 4s2(20) → 3d10(30) → 4p6(36) → 5s2(38) → 4d10(48) → 5p6(54) → 6s2(56) → 4f14(70) → 5d10(80) → 6p6(86) → 7s2(88) → 5f11(99)
Uses of einsteinium
Einsteinium is used for research only; it was first identified in the debris of the 1952 hydrogen bomb test.
Safety
Einsteinium is radioactive. Using, storing or transporting radioactive material requires a licence from the national regulator (BAPETEN in Indonesia). Always read the safety data sheet (SDS) before working with a chemical.
Other actinides
Frequently asked questions
What is the electron configuration of einsteinium?
The electron configuration of einsteinium (Es, atomic number 99) is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f11, or [Rn] 7s2 5f11 in short. By shell: 2, 8, 18, 32, 29, 8, 2.
How many valence electrons does einsteinium have?
Einsteinium has 2 electrons in its outer shell. For lanthanides and actinides, valence electrons are not assigned by the usual group rule.
Which group and period is einsteinium in?
Einsteinium is in the actinide series, period 7, f-block.
What is the atomic mass of einsteinium?
Einsteinium has no stable isotope, so the mass number of its longest-lived isotope, [252], is given.
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