Einsteinium (Es): electron configuration, atomic mass and facts
Einsteinium (Es) is element 99 of the periodic table, an actinide in period 7 (f-block). Its electron configuration is [Rn] 5f11 7s2, with electrons arranged in shells 2, 8, 18, 32, 29, 8, 2, and its most stable isotope has mass number 252.
💡 Named after Albert Einstein. First found in debris from a hydrogen-bomb test.
▶ Watch Einsteinium’s electrons orbit in the interactive periodic tableEinsteinium at a glance
| Symbol | Es |
|---|---|
| Atomic number | 99 |
| Atomic mass | [252] u (most stable isotope) |
| Category | Actinide |
| Group | f-block (no group number) |
| Period | 7 |
| Block | f-block |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 5f11 6s2 6p6 7s2 |
| Noble-gas shorthand | [Rn] 5f11 7s2 |
| Electrons per shell | 2, 8, 18, 32, 29, 8, 2 |
| Electronegativity (Pauling) | 1.3 |
| State at 20 °C | solid |
Where is Einsteinium on the periodic table?
Einsteinium is in period 7 of the f-block, the actinide row printed below the main table. It has 7 electron shells, and this row is where the 5f subshell fills.
How to work out the electron configuration of Einsteinium
Put 99 electrons into subshells in order of rising energy, filling each before starting the next: 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). In shorthand, [Rn] stands for the 86 electrons of radon, giving [Rn] 5f¹¹ 7s².
How electronegative is Einsteinium?
Einsteinium has a Pauling electronegativity of 1.3, ranking 62 of the 100 elements with a known value (fluorine is highest at 3.98). That is low: it tends to give up electrons and form positive ions.
Frequently asked questions
What is the electron configuration of Einsteinium?
The electron configuration of Einsteinium (Es) is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 5f11 6s2 6p6 7s2. In noble-gas shorthand it is written [Rn] 5f11 7s2.
How many electrons does Einsteinium have in each shell?
Einsteinium has 99 electrons arranged in shells as 2, 8, 18, 32, 29, 8, 2.
What is the atomic mass of Einsteinium?
Einsteinium has no stable isotopes. Its most stable isotope has a mass number of 252.
Is Einsteinium a metal?
Yes. Einsteinium is an actinide.
Explore nearby elements
More actinides: Curium, Berkelium, Californium, Fermium, Mendelevium, Nobelium. See all elements on the periodic table.