Astatine (At)
Astatine is element 85, a halogen in period 6, group 17 of the periodic table. At room temperature it is a solid.
Electron configuration [Xe] 4f14 5d10 6s2 6p5
Electrons per shell 2, 8, 18, 32, 18, 7
Astatine data
| Atomic number | 85 |
|---|---|
| Symbol | At |
| Atomic mass | [210] (mass number of the longest-lived isotope) |
| Category | Halogen |
| Group | 17 |
| Period | 6 |
| Block | p |
| State at 25 °C | solid |
| Melting point | 575 K (301.9 °C) |
| Boiling point | — |
| Density | — |
| Electronegativity (Pauling) | 2.2 |
| Atomic radius | — |
| 1st ionization energy | 920 kJ/mol |
| Electron affinity | -270 kJ/mol |
| Oxidation states | -1, +1, +3, +5 |
| Common ion charge | − |
| Discovered | 1940 |
Orbital diagram
Each box is one orbital holding up to two electrons of opposite spin. Following Hund’s rule, electrons spread out singly across a subshell before pairing.
Work through astatine’s configuration and its ions →
Where astatine sits
Astatine belongs to the halogens. Its Pauling electronegativity of 2.2 is mid-range; see the electronegativity chart and periodic trends for context. To use its mass in a calculation, try the molar mass calculator.
Astatine FAQ
What is the electron configuration of astatine?
Astatine (Z = 85) has the configuration 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 4f14 5d10 6s2 6p5. In noble-gas shorthand that is [Xe] 4f14 5d10 6s2 6p5.
How many valence electrons does astatine have?
7 (outer shell (n = 6)).
What is the atomic mass of astatine?
Astatine has no stable isotopes. Its most stable known isotope has mass number 210, so tables list [210].
Is astatine a metal?
No. Astatine is a halogen.
What is the charge of a astatine ion?
Astatine most commonly forms At−.