Astatine (At): Electron Configuration, Properties and Uses
Astatine (At): Electron Configuration, Properties and Uses
Electron configuration [Xe] 6s2 4f14 5d10 6p5 · group 17 · period 6 · Ar [210]
Astatine data
- Atomic number
- 85
- Relative atomic mass
- [210]
- Group
- 17
- Period
- 6
- Block
- p
- Category
- Halogen
- Electron configuration
- [Xe] 6s2 4f14 5d10 6p5
- Full configuration
- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p5
- Electrons per shell
- 2, 8, 18, 32, 18, 7 (K L M N O P)
- Valence electrons
- 7
- Electronegativity (Pauling)
- 2.2
- First ionisation energy
- 9.5 eV
- Atomic radius (van der Waals)
- 202 pm
- State at room temperature
- Solid
- Melting point
- 302 °C
- Boiling point
- no data
- Density
- 7 g/cm³
- Common oxidation states
- +7, +5, +3, +1, −1
- Discovered
- 1940
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 18 · P 7
Orbital diagram (outer electrons)
About astatine
With atomic number 85, astatine (At) has 85 protons in its nucleus and 85 electrons as a neutral atom. It is a halogen in group 17, period 6, p-block. The element was discovered in 1940. Astatine is a solid at room temperature, melting at 302 °C.
Astatine electron configuration
The electron configuration of astatine is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p5, or in short [Xe] 6s2 4f14 5d10 6p5. Its electrons occupy 6 shells: K = 2, L = 8, M = 18, N = 32, O = 18, P = 7. Astatine has 7 valence electrons in the P shell (6s2 6p5), which is why it sits in group 17.
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) → 6p5(85)
Uses of astatine
In industry and the laboratory, astatine turns up in many places, for example research on targeted alpha cancer therapy with At-211; one of the rarest naturally occurring elements in Earth’s crust.
Safety
Astatine 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 elements in group 17
Frequently asked questions
What is the electron configuration of astatine?
The electron configuration of astatine (At, atomic number 85) is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p5, or [Xe] 6s2 4f14 5d10 6p5 in short. By shell: 2, 8, 18, 32, 18, 7.
How many valence electrons does astatine have?
Astatine has 7 valence electrons.
Which group and period is astatine in?
Astatine is in group 17, period 6, p-block.
What is the atomic mass of astatine?
Astatine has no stable isotope, so the mass number of its longest-lived isotope, [210], is given.
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