Astatine (At): electron configuration, atomic mass and facts
Astatine (At) is element 85 of the periodic table, a halogen in period 6, group 17. Its electron configuration is [Xe] 4f14 5d10 6s2 6p5, with electrons arranged in shells 2, 8, 18, 32, 18, 7, and its most stable isotope has mass number 210.
▶ Watch Astatine’s electrons orbit in the interactive periodic tableAstatine at a glance
| Symbol | At |
|---|---|
| Atomic number | 85 |
| Atomic mass | [210] u (most stable isotope) |
| Category | Halogen |
| Group | 17 |
| Period | 6 |
| Block | p-block |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p5 |
| Noble-gas shorthand | [Xe] 4f14 5d10 6s2 6p5 |
| Electrons per shell | 2, 8, 18, 32, 18, 7 |
| Outer-shell electrons | 7 |
| Electronegativity (Pauling) | 2.2 |
| State at 20 °C | solid |
Where is Astatine on the periodic table?
Astatine is in period 6, group 17, in the p-block. The period number matches its 6 electron shells, and the block names the subshell its last electrons fill. In the same group, Iodine sits directly above it and Tennessine sits directly below it. Elements in one group have the same number of outer-shell electrons (7 here), which is why they react in similar ways.
How to work out the electron configuration of Astatine
Put 85 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), 6p⁵ (85). In shorthand, [Xe] stands for the 54 electrons of xenon, giving [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁵.
How electronegative is Astatine?
Astatine has a Pauling electronegativity of 2.2, ranking 17 of the 100 elements with a known value (fluorine is highest at 3.98). That is in the middle of the range.
Frequently asked questions
What is the electron configuration of Astatine?
The electron configuration of Astatine (At) is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p5. In noble-gas shorthand it is written [Xe] 4f14 5d10 6s2 6p5.
How many electrons does Astatine have in each shell?
Astatine has 85 electrons arranged in shells as 2, 8, 18, 32, 18, 7. It has 7 electrons in its outer shell.
What is the atomic mass of Astatine?
Astatine has no stable isotopes. Its most stable isotope has a mass number of 210.
Is Astatine a metal?
No. Astatine is a halogen.
Explore nearby elements
More halogens: Fluorine, Chlorine, Bromine, Iodine, Tennessine. See all elements on the periodic table.